summaryrefslogtreecommitdiffstats
path: root/doc/src/sgml/html/sql-createtable.html
blob: b6c4be023f478a9a6cc3284bed5ce4b9219fc830 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>CREATE TABLE</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION" /><link rel="next" href="sql-createtableas.html" title="CREATE TABLE AS" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE TABLE</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-createtableas.html" title="CREATE TABLE AS">Next</a></td></tr></table><hr /></div><div class="refentry" id="SQL-CREATETABLE"><div class="titlepage"></div><a id="id-1.9.3.85.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE TABLE</span></h2><p>CREATE TABLE — define a new table</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em> ( [
  { <em class="replaceable"><code>column_name</code></em> <em class="replaceable"><code>data_type</code></em> [ COMPRESSION <em class="replaceable"><code>compression_method</code></em> ] [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
    | <em class="replaceable"><code>table_constraint</code></em>
    | LIKE <em class="replaceable"><code>source_table</code></em> [ <em class="replaceable"><code>like_option</code></em> ... ] }
    [, ... ]
] )
[ INHERITS ( <em class="replaceable"><code>parent_table</code></em> [, ... ] ) ]
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ USING <em class="replaceable"><code>method</code></em> ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em>
    OF <em class="replaceable"><code>type_name</code></em> [ (
  { <em class="replaceable"><code>column_name</code></em> [ WITH OPTIONS ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
    | <em class="replaceable"><code>table_constraint</code></em> }
    [, ... ]
) ]
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ USING <em class="replaceable"><code>method</code></em> ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em>
    PARTITION OF <em class="replaceable"><code>parent_table</code></em> [ (
  { <em class="replaceable"><code>column_name</code></em> [ WITH OPTIONS ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
    | <em class="replaceable"><code>table_constraint</code></em> }
    [, ... ]
) ] { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ USING <em class="replaceable"><code>method</code></em> ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]

<span class="phrase">where <em class="replaceable"><code>column_constraint</code></em> is:</span>

[ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]
{ NOT NULL |
  NULL |
  CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |
  DEFAULT <em class="replaceable"><code>default_expr</code></em> |
  GENERATED ALWAYS AS ( <em class="replaceable"><code>generation_expr</code></em> ) STORED |
  GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ] |
  UNIQUE [ NULLS [ NOT ] DISTINCT ] <em class="replaceable"><code>index_parameters</code></em> |
  PRIMARY KEY <em class="replaceable"><code>index_parameters</code></em> |
  REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
    [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ] [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

<span class="phrase">and <em class="replaceable"><code>table_constraint</code></em> is:</span>

[ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]
{ CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |
  UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |
  PRIMARY KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |
  EXCLUDE [ USING <em class="replaceable"><code>index_method</code></em> ] ( <em class="replaceable"><code>exclude_element</code></em> WITH <em class="replaceable"><code>operator</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> [ WHERE ( <em class="replaceable"><code>predicate</code></em> ) ] |
  FOREIGN KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> [, ... ] ) ]
    [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ] [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

<span class="phrase">and <em class="replaceable"><code>like_option</code></em> is:</span>

{ INCLUDING | EXCLUDING } { COMMENTS | COMPRESSION | CONSTRAINTS | DEFAULTS | GENERATED | IDENTITY | INDEXES | STATISTICS | STORAGE | ALL }

<span class="phrase">and <em class="replaceable"><code>partition_bound_spec</code></em> is:</span>

IN ( <em class="replaceable"><code>partition_bound_expr</code></em> [, ...] ) |
FROM ( { <em class="replaceable"><code>partition_bound_expr</code></em> | MINVALUE | MAXVALUE } [, ...] )
  TO ( { <em class="replaceable"><code>partition_bound_expr</code></em> | MINVALUE | MAXVALUE } [, ...] ) |
WITH ( MODULUS <em class="replaceable"><code>numeric_literal</code></em>, REMAINDER <em class="replaceable"><code>numeric_literal</code></em> )

<span class="phrase"><em class="replaceable"><code>index_parameters</code></em> in <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>, and <code class="literal">EXCLUDE</code> constraints are:</span>

[ INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) ]
[ USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]

<span class="phrase"><em class="replaceable"><code>exclude_element</code></em> in an <code class="literal">EXCLUDE</code> constraint is:</span>

{ <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ <em class="replaceable"><code>opclass</code></em> ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]

<span class="phrase"><em class="replaceable"><code>referential_action</code></em> in a <code class="literal">FOREIGN KEY</code>/<code class="literal">REFERENCES</code> constraint is:</span>

{ NO ACTION | RESTRICT | CASCADE | SET NULL [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ] | SET DEFAULT [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ] }
</pre></div><div class="refsect1" id="SQL-CREATETABLE-DESCRIPTION"><h2>Description</h2><p>
   <code class="command">CREATE TABLE</code> will create a new, initially empty table
   in the current database. The table will be owned by the user issuing the
   command.
  </p><p>
   If a schema name is given (for example, <code class="literal">CREATE TABLE
   myschema.mytable ...</code>) then the table is created in the specified
   schema.  Otherwise it is created in the current schema.  Temporary
   tables exist in a special schema, so a schema name cannot be given
   when creating a temporary table.  The name of the table must be
   distinct from the name of any other relation (table, sequence, index, view,
   materialized view, or foreign table) in the same schema.
  </p><p>
   <code class="command">CREATE TABLE</code> also automatically creates a data
   type that represents the composite type corresponding
   to one row of the table.  Therefore, tables cannot have the same
   name as any existing data type in the same schema.
  </p><p>
   The optional constraint clauses specify constraints (tests) that
   new or updated rows must satisfy for an insert or update operation
   to succeed.  A constraint is an SQL object that helps define the
   set of valid values in the table in various ways.
  </p><p>
   There are two ways to define constraints: table constraints and
   column constraints.  A column constraint is defined as part of a
   column definition.  A table constraint definition is not tied to a
   particular column, and it can encompass more than one column.
   Every column constraint can also be written as a table constraint;
   a column constraint is only a notational convenience for use when the
   constraint only affects one column.
  </p><p>
   To be able to create a table, you must have <code class="literal">USAGE</code>
   privilege on all column types or the type in the <code class="literal">OF</code>
   clause, respectively.
  </p></div><div class="refsect1" id="id-1.9.3.85.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt id="SQL-CREATETABLE-TEMPORARY"><span class="term"><code class="literal">TEMPORARY</code> or <code class="literal">TEMP</code></span></dt><dd><p>
      If specified, the table is created as a temporary table.
      Temporary tables are automatically dropped at the end of a
      session, or optionally at the end of the current transaction
      (see <code class="literal">ON COMMIT</code> below).  The default
      search_path includes the temporary schema first and so identically
      named existing permanent tables are not chosen for new plans
      while the temporary table exists, unless they are referenced
      with schema-qualified names. Any indexes created on a temporary
      table are automatically temporary as well.
     </p><p>
      The <a class="link" href="routine-vacuuming.html#AUTOVACUUM" title="25.1.6. The Autovacuum Daemon">autovacuum daemon</a> cannot
      access and therefore cannot vacuum or analyze temporary tables.
      For this reason, appropriate vacuum and analyze operations should be
      performed via session SQL commands.  For example, if a temporary
      table is going to be used in complex queries, it is wise to run
      <code class="command">ANALYZE</code> on the temporary table after it is populated.
     </p><p>
      Optionally, <code class="literal">GLOBAL</code> or <code class="literal">LOCAL</code>
      can be written before <code class="literal">TEMPORARY</code> or <code class="literal">TEMP</code>.
      This presently makes no difference in <span class="productname">PostgreSQL</span>
      and is deprecated; see
      <a class="xref" href="sql-createtable.html#SQL-CREATETABLE-COMPATIBILITY" title="Compatibility">Compatibility</a> below.
     </p></dd><dt id="SQL-CREATETABLE-UNLOGGED"><span class="term"><code class="literal">UNLOGGED</code></span></dt><dd><p>
      If specified, the table is created as an unlogged table.  Data written
      to unlogged tables is not written to the write-ahead log (see <a class="xref" href="wal.html" title="Chapter 30. Reliability and the Write-Ahead Log">Chapter 30</a>), which makes them considerably faster than ordinary
      tables.  However, they are not crash-safe: an unlogged table is
      automatically truncated after a crash or unclean shutdown.  The contents
      of an unlogged table are also not replicated to standby servers.
      Any indexes created on an unlogged table are automatically unlogged as
      well.
     </p><p>
      If this is specified, any sequences created together with the unlogged
      table (for identity or serial columns) are also created as unlogged.
     </p></dd><dt><span class="term"><code class="literal">IF NOT EXISTS</code></span></dt><dd><p>
      Do not throw an error if a relation with the same name already exists.
      A notice is issued in this case.  Note that there is no guarantee that
      the existing relation is anything like the one that would have been
      created.
     </p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em></span></dt><dd><p>
      The name (optionally schema-qualified) of the table to be created.
     </p></dd><dt><span class="term"><code class="literal">OF <em class="replaceable"><code>type_name</code></em></code></span></dt><dd><p>
      Creates a <em class="firstterm">typed table</em>, which takes its
      structure from the specified composite type (name optionally
      schema-qualified).  A typed table is tied to its type; for
      example the table will be dropped if the type is dropped
      (with <code class="literal">DROP TYPE ... CASCADE</code>).
     </p><p>
      When a typed table is created, then the data types of the
      columns are determined by the underlying composite type and are
      not specified by the <code class="literal">CREATE TABLE</code> command.
      But the <code class="literal">CREATE TABLE</code> command can add defaults
      and constraints to the table and can specify storage parameters.
     </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>
      The name of a column to be created in the new table.
     </p></dd><dt><span class="term"><em class="replaceable"><code>data_type</code></em></span></dt><dd><p>
      The data type of the column. This can include array
      specifiers. For more information on the data types supported by
      <span class="productname">PostgreSQL</span>, refer to <a class="xref" href="datatype.html" title="Chapter 8. Data Types">Chapter 8</a>.
     </p></dd><dt><span class="term"><code class="literal">COLLATE <em class="replaceable"><code>collation</code></em></code></span></dt><dd><p>
      The <code class="literal">COLLATE</code> clause assigns a collation to
      the column (which must be of a collatable data type).
      If not specified, the column data type's default collation is used.
     </p></dd><dt><span class="term"><code class="literal">COMPRESSION <em class="replaceable"><code>compression_method</code></em></code></span></dt><dd><p>
      The <code class="literal">COMPRESSION</code> clause sets the compression method
      for the column.  Compression is supported only for variable-width data
      types, and is used only when the column's storage mode
      is <code class="literal">main</code> or <code class="literal">extended</code>.
      (See <a class="xref" href="sql-altertable.html" title="ALTER TABLE"><span class="refentrytitle">ALTER TABLE</span></a> for information on
      column storage modes.) Setting this property for a partitioned table
      has no direct effect, because such tables have no storage of their own,
      but the configured value will be inherited by newly-created partitions.
      The supported compression methods are <code class="literal">pglz</code> and
      <code class="literal">lz4</code>.  (<code class="literal">lz4</code> is available only if
      <code class="option">--with-lz4</code> was used when building
      <span class="productname">PostgreSQL</span>.)  In addition,
      <em class="replaceable"><code>compression_method</code></em>
      can be <code class="literal">default</code> to explicitly specify the default
      behavior, which is to consult the
      <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TOAST-COMPRESSION">default_toast_compression</a> setting at the time of
      data insertion to determine the method to use.
     </p></dd><dt><span class="term"><code class="literal">INHERITS ( <em class="replaceable"><code>parent_table</code></em> [, ... ] )</code></span></dt><dd><p>
      The optional <code class="literal">INHERITS</code> clause specifies a list of
      tables from which the new table automatically inherits all
      columns.  Parent tables can be plain tables or foreign tables.
     </p><p>
      Use of <code class="literal">INHERITS</code> creates a persistent relationship
      between the new child table and its parent table(s).  Schema
      modifications to the parent(s) normally propagate to children
      as well, and by default the data of the child table is included in
      scans of the parent(s).
     </p><p>
      If the same column name exists in more than one parent
      table, an error is reported unless the data types of the columns
      match in each of the parent tables.  If there is no conflict,
      then the duplicate columns are merged to form a single column in
      the new table.  If the column name list of the new table
      contains a column name that is also inherited, the data type must
      likewise match the inherited column(s), and the column
      definitions are merged into one.  If the
      new table explicitly specifies a default value for the column,
      this default overrides any defaults from inherited declarations
      of the column.  Otherwise, any parents that specify default
      values for the column must all specify the same default, or an
      error will be reported.
     </p><p>
      <code class="literal">CHECK</code> constraints are merged in essentially the same way as
      columns: if multiple parent tables and/or the new table definition
      contain identically-named <code class="literal">CHECK</code> constraints, these
      constraints must all have the same check expression, or an error will be
      reported.  Constraints having the same name and expression will
      be merged into one copy.  A constraint marked <code class="literal">NO INHERIT</code> in a
      parent will not be considered.  Notice that an unnamed <code class="literal">CHECK</code>
      constraint in the new table will never be merged, since a unique name
      will always be chosen for it.
     </p><p>
      Column <code class="literal">STORAGE</code> settings are also copied from parent tables.
     </p><p>
      If a column in the parent table is an identity column, that property is
      not inherited.  A column in the child table can be declared identity
      column if desired.
     </p></dd><dt><span class="term"><code class="literal">PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ <em class="replaceable"><code>opclass</code></em> ] [, ...] ) </code></span></dt><dd><p>
      The optional <code class="literal">PARTITION BY</code> clause specifies a strategy
      of partitioning the table.  The table thus created is called a
      <em class="firstterm">partitioned</em> table.  The parenthesized list of
      columns or expressions forms the <em class="firstterm">partition key</em>
      for the table.  When using range or hash partitioning, the partition key
      can include multiple columns or expressions (up to 32, but this limit can
      be altered when building <span class="productname">PostgreSQL</span>), but for
      list partitioning, the partition key must consist of a single column or
      expression.
     </p><p>
      Range and list partitioning require a btree operator class, while hash
      partitioning requires a hash operator class.  If no operator class is
      specified explicitly, the default operator class of the appropriate
      type will be used; if no default operator class exists, an error will
      be raised.  When hash partitioning is used, the operator class used
      must implement support function 2 (see <a class="xref" href="xindex.html#XINDEX-SUPPORT" title="38.16.3. Index Method Support Routines">Section 38.16.3</a>
      for details).
     </p><p>
      A partitioned table is divided into sub-tables (called partitions),
      which are created using separate <code class="literal">CREATE TABLE</code> commands.
      The partitioned table is itself empty.  A data row inserted into the
      table is routed to a partition based on the value of columns or
      expressions in the partition key.  If no existing partition matches
      the values in the new row, an error will be reported.
     </p><p>
      Partitioned tables do not support <code class="literal">EXCLUDE</code> constraints;
      however, you can define these constraints on individual partitions.
     </p><p>
      See <a class="xref" href="ddl-partitioning.html" title="5.11. Table Partitioning">Section 5.11</a> for more discussion on table
      partitioning.
     </p></dd><dt id="SQL-CREATETABLE-PARTITION"><span class="term"><code class="literal">PARTITION OF <em class="replaceable"><code>parent_table</code></em> { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }</code></span></dt><dd><p>
      Creates the table as a <em class="firstterm">partition</em> of the specified
      parent table. The table can be created either as a partition for specific
      values using <code class="literal">FOR VALUES</code> or as a default partition
      using <code class="literal">DEFAULT</code>.  Any indexes, constraints and
      user-defined row-level triggers that exist in the parent table are cloned
      on the new partition.
     </p><p>
      The <em class="replaceable"><code>partition_bound_spec</code></em>
      must correspond to the partitioning method and partition key of the
      parent table, and must not overlap with any existing partition of that
      parent.  The form with <code class="literal">IN</code> is used for list partitioning,
      the form with <code class="literal">FROM</code> and <code class="literal">TO</code> is used
      for range partitioning, and the form with <code class="literal">WITH</code> is used
      for hash partitioning.
     </p><p>
      <em class="replaceable"><code>partition_bound_expr</code></em> is
      any variable-free expression (subqueries, window functions, aggregate
      functions, and set-returning functions are not allowed).  Its data type
      must match the data type of the corresponding partition key column.
      The expression is evaluated once at table creation time, so it can
      even contain volatile expressions such as
      <code class="literal"><code class="function">CURRENT_TIMESTAMP</code></code>.
     </p><p>
      When creating a list partition, <code class="literal">NULL</code> can be
      specified to signify that the partition allows the partition key
      column to be null.  However, there cannot be more than one such
      list partition for a given parent table.  <code class="literal">NULL</code>
      cannot be specified for range partitions.
     </p><p>
      When creating a range partition, the lower bound specified with
      <code class="literal">FROM</code> is an inclusive bound, whereas the upper
      bound specified with <code class="literal">TO</code> is an exclusive bound.
      That is, the values specified in the <code class="literal">FROM</code> list
      are valid values of the corresponding partition key columns for this
      partition, whereas those in the <code class="literal">TO</code> list are
      not.  Note that this statement must be understood according to the
      rules of row-wise comparison (<a class="xref" href="functions-comparisons.html#ROW-WISE-COMPARISON" title="9.24.5. Row Constructor Comparison">Section 9.24.5</a>).
      For example, given <code class="literal">PARTITION BY RANGE (x,y)</code>, a partition
      bound <code class="literal">FROM (1, 2) TO (3, 4)</code>
      allows <code class="literal">x=1</code> with any <code class="literal">y&gt;=2</code>,
      <code class="literal">x=2</code> with any non-null <code class="literal">y</code>,
      and <code class="literal">x=3</code> with any <code class="literal">y&lt;4</code>.
     </p><p>
      The special values <code class="literal">MINVALUE</code> and <code class="literal">MAXVALUE</code>
      may be used when creating a range partition to indicate that there
      is no lower or upper bound on the column's value. For example, a
      partition defined using <code class="literal">FROM (MINVALUE) TO (10)</code> allows
      any values less than 10, and a partition defined using
      <code class="literal">FROM (10) TO (MAXVALUE)</code> allows any values greater than
      or equal to 10.
     </p><p>
      When creating a range partition involving more than one column, it
      can also make sense to use <code class="literal">MAXVALUE</code> as part of the lower
      bound, and <code class="literal">MINVALUE</code> as part of the upper bound. For
      example, a partition defined using
      <code class="literal">FROM (0, MAXVALUE) TO (10, MAXVALUE)</code> allows any rows
      where the first partition key column is greater than 0 and less than
      or equal to 10. Similarly, a partition defined using
      <code class="literal">FROM ('a', MINVALUE) TO ('b', MINVALUE)</code> allows any rows
      where the first partition key column starts with "a".
     </p><p>
      Note that if <code class="literal">MINVALUE</code> or <code class="literal">MAXVALUE</code> is used for
      one column of a partitioning bound, the same value must be used for all
      subsequent columns.  For example, <code class="literal">(10, MINVALUE, 0)</code> is not
      a valid bound; you should write <code class="literal">(10, MINVALUE, MINVALUE)</code>.
     </p><p>
      Also note that some element types, such as <code class="literal">timestamp</code>,
      have a notion of "infinity", which is just another value that can
      be stored. This is different from <code class="literal">MINVALUE</code> and
      <code class="literal">MAXVALUE</code>, which are not real values that can be stored,
      but rather they are ways of saying that the value is unbounded.
      <code class="literal">MAXVALUE</code> can be thought of as being greater than any
      other value, including "infinity" and <code class="literal">MINVALUE</code> as being
      less than any other value, including "minus infinity". Thus the range
      <code class="literal">FROM ('infinity') TO (MAXVALUE)</code> is not an empty range; it
      allows precisely one value to be stored — "infinity".
     </p><p>
      If <code class="literal">DEFAULT</code> is specified, the table will be
      created as the default partition of the parent table.  This option
      is not available for hash-partitioned tables.  A partition key value
      not fitting into any other partition of the given parent will be
      routed to the default partition.
     </p><p>
      When a table has an existing <code class="literal">DEFAULT</code> partition and
      a new partition is added to it, the default partition must
      be scanned to verify that it does not contain any rows which properly
      belong in the new partition.  If the default partition contains a
      large number of rows, this may be slow.  The scan will be skipped if
      the default partition is a foreign table or if it has a constraint which
      proves that it cannot contain rows which should be placed in the new
      partition.
     </p><p>
      When creating a hash partition, a modulus and remainder must be specified.
      The modulus must be a positive integer, and the remainder must be a
      non-negative integer less than the modulus.  Typically, when initially
      setting up a hash-partitioned table, you should choose a modulus equal to
      the number of partitions and assign every table the same modulus and a
      different remainder (see examples, below).   However, it is not required
      that every partition have the same modulus, only that every modulus which
      occurs among the partitions of a hash-partitioned table is a factor of the
      next larger modulus.  This allows the number of partitions to be increased
      incrementally without needing to move all the data at once.  For example,
      suppose you have a hash-partitioned table with 8 partitions, each of which
      has modulus 8, but find it necessary to increase the number of partitions
      to 16.  You can detach one of the modulus-8 partitions, create two new
      modulus-16 partitions covering the same portion of the key space (one with
      a remainder equal to the remainder of the detached partition, and the
      other with a remainder equal to that value plus 8), and repopulate them
      with data.  You can then repeat this -- perhaps at a later time -- for
      each modulus-8 partition until none remain.  While this may still involve
      a large amount of data movement at each step, it is still better than
      having to create a whole new table and move all the data at once.
     </p><p>
      A partition must have the same column names and types as the partitioned
      table to which it belongs. Modifications to the column names or types of
      a partitioned table will automatically propagate to all partitions.
      <code class="literal">CHECK</code> constraints will be inherited automatically by
      every partition, but an individual partition may specify additional
      <code class="literal">CHECK</code> constraints; additional constraints with the
      same name and condition as in the parent will be merged with the parent
      constraint.  Defaults may be specified separately for each partition.
      But note that a partition's default value is not applied when inserting
      a tuple through a partitioned table.
     </p><p>
      Rows inserted into a partitioned table will be automatically routed to
      the correct partition.  If no suitable partition exists, an error will
      occur.
     </p><p>
      Operations such as <code class="command">TRUNCATE</code>
      which normally affect a table and all of its
      inheritance children will cascade to all partitions, but may also be
      performed on an individual partition.
     </p><p>
      Note that creating a partition using <code class="literal">PARTITION OF</code>
      requires taking an <code class="literal">ACCESS EXCLUSIVE</code> lock on the
      parent partitioned table.  Likewise, dropping a partition
      with <code class="command">DROP TABLE</code> requires taking
      an <code class="literal">ACCESS EXCLUSIVE</code> lock on the parent table.
      It is possible to use <a class="link" href="sql-altertable.html" title="ALTER TABLE"><code class="command">ALTER
      TABLE ATTACH/DETACH PARTITION</code></a> to perform these
      operations with a weaker lock, thus reducing interference with
      concurrent operations on the partitioned table.
     </p></dd><dt><span class="term"><code class="literal">LIKE <em class="replaceable"><code>source_table</code></em> [ <em class="replaceable"><code>like_option</code></em> ... ]</code></span></dt><dd><p>
      The <code class="literal">LIKE</code> clause specifies a table from which
      the new table automatically copies all column names, their data types,
      and their not-null constraints.
     </p><p>
      Unlike <code class="literal">INHERITS</code>, the new table and original table
      are completely decoupled after creation is complete.  Changes to the
      original table will not be applied to the new table, and it is not
      possible to include data of the new table in scans of the original
      table.
     </p><p>
      Also unlike <code class="literal">INHERITS</code>, columns and
      constraints copied by <code class="literal">LIKE</code> are not merged with similarly
      named columns and constraints.
      If the same name is specified explicitly or in another
      <code class="literal">LIKE</code> clause, an error is signaled.
     </p><p>
      The optional <em class="replaceable"><code>like_option</code></em> clauses specify
      which additional properties of the original table to copy.  Specifying
      <code class="literal">INCLUDING</code> copies the property, specifying
      <code class="literal">EXCLUDING</code> omits the property.
      <code class="literal">EXCLUDING</code> is the default.  If multiple specifications
      are made for the same kind of object, the last one is used.  The
      available options are:

      </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">INCLUDING COMMENTS</code></span></dt><dd><p>
          Comments for the copied columns, constraints, and indexes will be
          copied.  The default behavior is to exclude comments, resulting in
          the copied columns and constraints in the new table having no
          comments.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING COMPRESSION</code></span></dt><dd><p>
          Compression method of the columns will be copied.  The default
          behavior is to exclude compression methods, resulting in columns
          having the default compression method.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING CONSTRAINTS</code></span></dt><dd><p>
          <code class="literal">CHECK</code> constraints will be copied.  No distinction
          is made between column constraints and table constraints.  Not-null
          constraints are always copied to the new table.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING DEFAULTS</code></span></dt><dd><p>
          Default expressions for the copied column definitions will be
          copied.  Otherwise, default expressions are not copied, resulting in
          the copied columns in the new table having null defaults.  Note that
          copying defaults that call database-modification functions, such as
          <code class="function">nextval</code>, may create a functional linkage
          between the original and new tables.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING GENERATED</code></span></dt><dd><p>
          Any generation expressions of copied column definitions will be
          copied.  By default, new columns will be regular base columns.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING IDENTITY</code></span></dt><dd><p>
          Any identity specifications of copied column definitions will be
          copied.  A new sequence is created for each identity column of the
          new table, separate from the sequences associated with the old
          table.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING INDEXES</code></span></dt><dd><p>
          Indexes, <code class="literal">PRIMARY KEY</code>, <code class="literal">UNIQUE</code>,
          and <code class="literal">EXCLUDE</code> constraints on the original table
          will be created on the new table.  Names for the new indexes and
          constraints are chosen according to the default rules, regardless of
          how the originals were named.  (This behavior avoids possible
          duplicate-name failures for the new indexes.)
         </p></dd><dt><span class="term"><code class="literal">INCLUDING STATISTICS</code></span></dt><dd><p>
          Extended statistics are copied to the new table.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING STORAGE</code></span></dt><dd><p>
          <code class="literal">STORAGE</code> settings for the copied column
          definitions will be copied.  The default behavior is to exclude
          <code class="literal">STORAGE</code> settings, resulting in the copied columns
          in the new table having type-specific default settings.  For more on
          <code class="literal">STORAGE</code> settings, see <a class="xref" href="storage-toast.html" title="73.2. TOAST">Section 73.2</a>.
         </p></dd><dt><span class="term"><code class="literal">INCLUDING ALL</code></span></dt><dd><p>
          <code class="literal">INCLUDING ALL</code> is an abbreviated form selecting
          all the available individual options.  (It could be useful to write
          individual <code class="literal">EXCLUDING</code> clauses after
          <code class="literal">INCLUDING ALL</code> to select all but some specific
          options.)
         </p></dd></dl></div><p>
     </p><p>
      The <code class="literal">LIKE</code> clause can also be used to copy column
      definitions from views, foreign tables, or composite types.
      Inapplicable options (e.g., <code class="literal">INCLUDING INDEXES</code> from
      a view) are ignored.
     </p></dd><dt><span class="term"><code class="literal">CONSTRAINT <em class="replaceable"><code>constraint_name</code></em></code></span></dt><dd><p>
      An optional name for a column or table constraint.  If the
      constraint is violated, the constraint name is present in error messages,
      so constraint names like <code class="literal">col must be positive</code> can be used
      to communicate helpful constraint information to client applications.
      (Double-quotes are needed to specify constraint names that contain spaces.)
      If a constraint name is not specified, the system generates a name.
     </p></dd><dt><span class="term"><code class="literal">NOT NULL</code></span></dt><dd><p>
      The column is not allowed to contain null values.
     </p></dd><dt><span class="term"><code class="literal">NULL</code></span></dt><dd><p>
      The column is allowed to contain null values. This is the default.
     </p><p>
      This clause is only provided for compatibility with
      non-standard SQL databases.  Its use is discouraged in new
      applications.
     </p></dd><dt><span class="term"><code class="literal">CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] </code></span></dt><dd><p>
      The <code class="literal">CHECK</code> clause specifies an expression producing a
      Boolean result which new or updated rows must satisfy for an
      insert or update operation to succeed.  Expressions evaluating
      to TRUE or UNKNOWN succeed.  Should any row of an insert or
      update operation produce a FALSE result, an error exception is
      raised and the insert or update does not alter the database.  A
      check constraint specified as a column constraint should
      reference that column's value only, while an expression
      appearing in a table constraint can reference multiple columns.
     </p><p>
      Currently, <code class="literal">CHECK</code> expressions cannot contain
      subqueries nor refer to variables other than columns of the
      current row (see <a class="xref" href="ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS" title="5.4.1. Check Constraints">Section 5.4.1</a>).
      The system column <code class="literal">tableoid</code>
      may be referenced, but not any other system column.
     </p><p>
      A constraint marked with <code class="literal">NO INHERIT</code> will not propagate to
      child tables.
     </p><p>
      When a table has multiple <code class="literal">CHECK</code> constraints,
      they will be tested for each row in alphabetical order by name,
      after checking <code class="literal">NOT NULL</code> constraints.
      (<span class="productname">PostgreSQL</span> versions before 9.5 did not honor any
      particular firing order for <code class="literal">CHECK</code> constraints.)
     </p></dd><dt><span class="term"><code class="literal">DEFAULT
    <em class="replaceable"><code>default_expr</code></em></code></span></dt><dd><p>
      The <code class="literal">DEFAULT</code> clause assigns a default data value for
      the column whose column definition it appears within.  The value
      is any variable-free expression (in particular, cross-references
      to other columns in the current table are not allowed).  Subqueries
      are not allowed either.  The data type of the default expression must
      match the data type of the column.
     </p><p>
      The default expression will be used in any insert operation that
      does not specify a value for the column.  If there is no default
      for a column, then the default is null.
     </p></dd><dt><span class="term"><code class="literal">GENERATED ALWAYS AS ( <em class="replaceable"><code>generation_expr</code></em> ) STORED</code><a id="id-1.9.3.85.6.2.19.1.2" class="indexterm"></a></span></dt><dd><p>
      This clause creates the column as a <em class="firstterm">generated
      column</em>.  The column cannot be written to, and when read the
      result of the specified expression will be returned.
     </p><p>
      The keyword <code class="literal">STORED</code> is required to signify that the
      column will be computed on write and will be stored on disk.
     </p><p>
      The generation expression can refer to other columns in the table, but
      not other generated columns.  Any functions and operators used must be
      immutable.  References to other tables are not allowed.
     </p></dd><dt><span class="term"><code class="literal">GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ]</code></span></dt><dd><p>
      This clause creates the column as an <em class="firstterm">identity
      column</em>.  It will have an implicit sequence attached to it
      and the column in new rows will automatically have values from the
      sequence assigned to it.
      Such a column is implicitly <code class="literal">NOT NULL</code>.
     </p><p>
      The clauses <code class="literal">ALWAYS</code> and <code class="literal">BY DEFAULT</code>
      determine how explicitly user-specified values are handled in
      <code class="command">INSERT</code> and <code class="command">UPDATE</code> commands.
     </p><p>
      In an <code class="command">INSERT</code> command, if <code class="literal">ALWAYS</code> is
      selected, a user-specified value is only accepted if the
      <code class="command">INSERT</code> statement specifies <code class="literal">OVERRIDING SYSTEM
      VALUE</code>.  If <code class="literal">BY DEFAULT</code> is selected, then the
      user-specified value takes precedence.  See <a class="xref" href="sql-insert.html" title="INSERT"><span class="refentrytitle">INSERT</span></a>
      for details.  (In the <code class="command">COPY</code> command, user-specified
      values are always used regardless of this setting.)
     </p><p>
      In an <code class="command">UPDATE</code> command, if <code class="literal">ALWAYS</code> is
      selected, any update of the column to any value other than
      <code class="literal">DEFAULT</code> will be rejected.  If <code class="literal">BY
      DEFAULT</code> is selected, the column can be updated normally.
      (There is no <code class="literal">OVERRIDING</code> clause for the
      <code class="command">UPDATE</code> command.)
     </p><p>
      The optional <em class="replaceable"><code>sequence_options</code></em> clause can be
      used to override the options of the sequence.
      See <a class="xref" href="sql-createsequence.html" title="CREATE SEQUENCE"><span class="refentrytitle">CREATE SEQUENCE</span></a> for details.
     </p></dd><dt><span class="term"><code class="literal">UNIQUE [ NULLS [ NOT ] DISTINCT ]</code> (column constraint)<br /></span><span class="term"><code class="literal">UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <em class="replaceable"><code>column_name</code></em> [, ... ] )</code>
    [<span class="optional"> <code class="literal">INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ...])</code> </span>] (table constraint)</span></dt><dd><p>
      The <code class="literal">UNIQUE</code> constraint specifies that a
      group of one or more columns of a table can contain
      only unique values. The behavior of a unique table constraint
      is the same as that of a unique column constraint, with the
      additional capability to span multiple columns.  The constraint
      therefore enforces that any two rows must differ in at least one
      of these columns.
     </p><p>
      For the purpose of a unique constraint, null values are not
      considered equal, unless <code class="literal">NULLS NOT DISTINCT</code> is
      specified.
     </p><p>
      Each unique constraint should name a set of columns that is
      different from the set of columns named by any other unique or
      primary key constraint defined for the table.  (Otherwise, redundant
      unique constraints will be discarded.)
     </p><p>
      When establishing a unique constraint for a multi-level partition
      hierarchy, all the columns in the partition key of the target
      partitioned table, as well as those of all its descendant partitioned
      tables, must be included in the constraint definition.
     </p><p>
      Adding a unique constraint will automatically create a unique btree
      index on the column or group of columns used in the constraint.
     </p><p>
      The optional <code class="literal">INCLUDE</code> clause adds to that index
      one or more columns that are simply <span class="quote"><span class="quote">payload</span></span>: uniqueness
      is not enforced on them, and the index cannot be searched on the basis
      of those columns.  However they can be retrieved by an index-only scan.
      Note that although the constraint is not enforced on included columns,
      it still depends on them.  Consequently, some operations on such columns
      (e.g., <code class="literal">DROP COLUMN</code>) can cause cascaded constraint and
      index deletion.
     </p></dd><dt><span class="term"><code class="literal">PRIMARY KEY</code> (column constraint)<br /></span><span class="term"><code class="literal">PRIMARY KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] )</code>
    [<span class="optional"> <code class="literal">INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ...])</code> </span>] (table constraint)</span></dt><dd><p>
      The <code class="literal">PRIMARY KEY</code> constraint specifies that a column or
      columns of a table can contain only unique (non-duplicate), nonnull
      values. Only one primary key can be specified for a table, whether as a
      column constraint or a table constraint.
     </p><p>
      The primary key constraint should name a set of columns that is
      different from the set of columns named by any unique
      constraint defined for the same table.  (Otherwise, the unique
      constraint is redundant and will be discarded.)
     </p><p>
      <code class="literal">PRIMARY KEY</code> enforces the same data constraints as
      a combination of <code class="literal">UNIQUE</code> and <code class="literal">NOT
      NULL</code>.  However,
      identifying a set of columns as the primary key also provides metadata
      about the design of the schema, since a primary key implies that other
      tables can rely on this set of columns as a unique identifier for rows.
     </p><p>
      When placed on a partitioned table, <code class="literal">PRIMARY KEY</code>
      constraints share the restrictions previously described
      for <code class="literal">UNIQUE</code> constraints.
     </p><p>
      Adding a <code class="literal">PRIMARY KEY</code> constraint will automatically
      create a unique btree index on the column or group of columns used in the
      constraint.
     </p><p>
      The optional <code class="literal">INCLUDE</code> clause adds to that index
      one or more columns that are simply <span class="quote"><span class="quote">payload</span></span>: uniqueness
      is not enforced on them, and the index cannot be searched on the basis
      of those columns.  However they can be retrieved by an index-only scan.
      Note that although the constraint is not enforced on included columns,
      it still depends on them.  Consequently, some operations on such columns
      (e.g., <code class="literal">DROP COLUMN</code>) can cause cascaded constraint and
      index deletion.
     </p></dd><dt id="SQL-CREATETABLE-EXCLUDE"><span class="term"><code class="literal">EXCLUDE [ USING <em class="replaceable"><code>index_method</code></em> ] ( <em class="replaceable"><code>exclude_element</code></em> WITH <em class="replaceable"><code>operator</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> [ WHERE ( <em class="replaceable"><code>predicate</code></em> ) ]</code></span></dt><dd><p>
      The <code class="literal">EXCLUDE</code> clause defines an exclusion
      constraint, which guarantees that if
      any two rows are compared on the specified column(s) or
      expression(s) using the specified operator(s), not all of these
      comparisons will return <code class="literal">TRUE</code>.  If all of the
      specified operators test for equality, this is equivalent to a
      <code class="literal">UNIQUE</code> constraint, although an ordinary unique constraint
      will be faster.  However, exclusion constraints can specify
      constraints that are more general than simple equality.
      For example, you can specify a constraint that
      no two rows in the table contain overlapping circles
      (see <a class="xref" href="datatype-geometric.html" title="8.8. Geometric Types">Section 8.8</a>) by using the
      <code class="literal">&amp;&amp;</code> operator.
     </p><p>
      Exclusion constraints are implemented using
      an index, so each specified operator must be associated with an
      appropriate operator class
      (see <a class="xref" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Section 11.10</a>) for the index access
      method <em class="replaceable"><code>index_method</code></em>.
      The operators are required to be commutative.
      Each <em class="replaceable"><code>exclude_element</code></em>
      can optionally specify an operator class and/or ordering options;
      these are described fully under
      <a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>.
     </p><p>
      The access method must support <code class="literal">amgettuple</code> (see <a class="xref" href="indexam.html" title="Chapter 64. Index Access Method Interface Definition">Chapter 64</a>); at present this means <acronym class="acronym">GIN</acronym>
      cannot be used.  Although it's allowed, there is little point in using
      B-tree or hash indexes with an exclusion constraint, because this
      does nothing that an ordinary unique constraint doesn't do better.
      So in practice the access method will always be <acronym class="acronym">GiST</acronym> or
      <acronym class="acronym">SP-GiST</acronym>.
     </p><p>
      The <em class="replaceable"><code>predicate</code></em> allows you to specify an
      exclusion constraint on a subset of the table; internally this creates a
      partial index. Note that parentheses are required around the predicate.
     </p></dd><dt><span class="term"><code class="literal">REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> ) ] [ MATCH <em class="replaceable"><code>matchtype</code></em> ] [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ] [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ]</code> (column constraint)<br /></span><span class="term"><code class="literal">FOREIGN KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] )
    REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> [, ... ] ) ]
    [ MATCH <em class="replaceable"><code>matchtype</code></em> ]
    [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ]
    [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ]</code>
    (table constraint)</span></dt><dd><p>
      These clauses specify a foreign key constraint, which requires
      that a group of one or more columns of the new table must only
      contain values that match values in the referenced
      column(s) of some row of the referenced table.  If the <em class="replaceable"><code>refcolumn</code></em> list is omitted, the
      primary key of the <em class="replaceable"><code>reftable</code></em>
      is used.  The referenced columns must be the columns of a non-deferrable
      unique or primary key constraint in the referenced table.  The user
      must have <code class="literal">REFERENCES</code> permission on the referenced table
      (either the whole table, or the specific referenced columns).  The
      addition of a foreign key constraint requires a
      <code class="literal">SHARE ROW EXCLUSIVE</code> lock on the referenced table.
      Note that foreign key constraints cannot be defined between temporary
      tables and permanent tables.
     </p><p>
      A value inserted into the referencing column(s) is matched against the
      values of the referenced table and referenced columns using the
      given match type.  There are three match types: <code class="literal">MATCH
      FULL</code>, <code class="literal">MATCH PARTIAL</code>, and <code class="literal">MATCH
      SIMPLE</code> (which is the default).  <code class="literal">MATCH
      FULL</code> will not allow one column of a multicolumn foreign key
      to be null unless all foreign key columns are null; if they are all
      null, the row is not required to have a match in the referenced table.
      <code class="literal">MATCH SIMPLE</code> allows any of the foreign key columns
      to be null; if any of them are null, the row is not required to have a
      match in the referenced table.
      <code class="literal">MATCH PARTIAL</code> is not yet implemented.
      (Of course, <code class="literal">NOT NULL</code> constraints can be applied to the
      referencing column(s) to prevent these cases from arising.)
     </p><p>
      In addition, when the data in the referenced columns is changed,
      certain actions are performed on the data in this table's
      columns.  The <code class="literal">ON DELETE</code> clause specifies the
      action to perform when a referenced row in the referenced table is
      being deleted.  Likewise, the <code class="literal">ON UPDATE</code>
      clause specifies the action to perform when a referenced column
      in the referenced table is being updated to a new value. If the
      row is updated, but the referenced column is not actually
      changed, no action is done. Referential actions other than the
      <code class="literal">NO ACTION</code> check cannot be deferred, even if
      the constraint is declared deferrable. There are the following possible
      actions for each clause:

      </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">NO ACTION</code></span></dt><dd><p>
          Produce an error indicating that the deletion or update
          would create a foreign key constraint violation.
          If the constraint is deferred, this
          error will be produced at constraint check time if there still
          exist any referencing rows.  This is the default action.
         </p></dd><dt><span class="term"><code class="literal">RESTRICT</code></span></dt><dd><p>
          Produce an error indicating that the deletion or update
          would create a foreign key constraint violation.
          This is the same as <code class="literal">NO ACTION</code> except that
          the check is not deferrable.
         </p></dd><dt><span class="term"><code class="literal">CASCADE</code></span></dt><dd><p>
          Delete any rows referencing the deleted row, or update the
          values of the referencing column(s) to the new values of the
          referenced columns, respectively.
         </p></dd><dt><span class="term"><code class="literal">SET NULL [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]</code></span></dt><dd><p>
          Set all of the referencing columns, or a specified subset of the
          referencing columns, to null. A subset of columns can only be
          specified for <code class="literal">ON DELETE</code> actions.
         </p></dd><dt><span class="term"><code class="literal">SET DEFAULT [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]</code></span></dt><dd><p>
          Set all of the referencing columns, or a specified subset of the
          referencing columns, to their default values. A subset of columns
          can only be specified for <code class="literal">ON DELETE</code> actions.
          (There must be a row in the referenced table matching the default
          values, if they are not null, or the operation will fail.)
         </p></dd></dl></div><p>
     </p><p>
      If the referenced column(s) are changed frequently, it might be wise to
      add an index to the referencing column(s) so that referential actions
      associated with the foreign key constraint can be performed more
      efficiently.
     </p></dd><dt><span class="term"><code class="literal">DEFERRABLE</code><br /></span><span class="term"><code class="literal">NOT DEFERRABLE</code></span></dt><dd><p>
      This controls whether the constraint can be deferred.  A
      constraint that is not deferrable will be checked immediately
      after every command.  Checking of constraints that are
      deferrable can be postponed until the end of the transaction
      (using the <a class="link" href="sql-set-constraints.html" title="SET CONSTRAINTS"><code class="command">SET CONSTRAINTS</code></a> command).
      <code class="literal">NOT DEFERRABLE</code> is the default.
      Currently, only <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>,
      <code class="literal">EXCLUDE</code>, and
      <code class="literal">REFERENCES</code> (foreign key) constraints accept this
      clause.  <code class="literal">NOT NULL</code> and <code class="literal">CHECK</code> constraints are not
      deferrable.  Note that deferrable constraints cannot be used as
      conflict arbitrators in an <code class="command">INSERT</code> statement that
      includes an <code class="literal">ON CONFLICT DO UPDATE</code> clause.
     </p></dd><dt><span class="term"><code class="literal">INITIALLY IMMEDIATE</code><br /></span><span class="term"><code class="literal">INITIALLY DEFERRED</code></span></dt><dd><p>
      If a constraint is deferrable, this clause specifies the default
      time to check the constraint.  If the constraint is
      <code class="literal">INITIALLY IMMEDIATE</code>, it is checked after each
      statement. This is the default.  If the constraint is
      <code class="literal">INITIALLY DEFERRED</code>, it is checked only at the
      end of the transaction.  The constraint check time can be
      altered with the <a class="link" href="sql-set-constraints.html" title="SET CONSTRAINTS"><code class="command">SET CONSTRAINTS</code></a> command.
     </p></dd><dt id="SQL-CREATETABLE-METHOD"><span class="term"><code class="literal">USING <em class="replaceable"><code>method</code></em></code></span></dt><dd><p>
      This optional clause specifies the table access method to use to store
      the contents for the new table; the method needs be an access method of
      type <code class="literal">TABLE</code>. See <a class="xref" href="tableam.html" title="Chapter 63. Table Access Method Interface Definition">Chapter 63</a> for more
      information.  If this option is not specified, the default table access
      method is chosen for the new table. See <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLE-ACCESS-METHOD">default_table_access_method</a> for more information.
     </p></dd><dt><span class="term"><code class="literal">WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] )</code></span></dt><dd><p>
      This clause specifies optional storage parameters for a table or index;
      see <a class="xref" href="sql-createtable.html#SQL-CREATETABLE-STORAGE-PARAMETERS" title="Storage Parameters">Storage Parameters</a> below for more
      information.  For backward-compatibility the <code class="literal">WITH</code>
      clause for a table can also include <code class="literal">OIDS=FALSE</code> to
      specify that rows of the new table should not contain OIDs (object
      identifiers), <code class="literal">OIDS=TRUE</code> is not supported anymore.
     </p></dd><dt><span class="term"><code class="literal">WITHOUT OIDS</code></span></dt><dd><p>
      This is backward-compatible syntax for declaring a table
      <code class="literal">WITHOUT OIDS</code>, creating a table <code class="literal">WITH
      OIDS</code> is not supported anymore.
     </p></dd><dt><span class="term"><code class="literal">ON COMMIT</code></span></dt><dd><p>
      The behavior of temporary tables at the end of a transaction
      block can be controlled using <code class="literal">ON COMMIT</code>.
      The three options are:

      </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">PRESERVE ROWS</code></span></dt><dd><p>
          No special action is taken at the ends of transactions.
          This is the default behavior.
         </p></dd><dt><span class="term"><code class="literal">DELETE ROWS</code></span></dt><dd><p>
          All rows in the temporary table will be deleted at the end
          of each transaction block.  Essentially, an automatic <a class="link" href="sql-truncate.html" title="TRUNCATE"><code class="command">TRUNCATE</code></a> is done
          at each commit.  When used on a partitioned table, this
          is not cascaded to its partitions.
         </p></dd><dt><span class="term"><code class="literal">DROP</code></span></dt><dd><p>
          The temporary table will be dropped at the end of the current
          transaction block.  When used on a partitioned table, this action
          drops its partitions and when used on tables with inheritance
          children, it drops the dependent children.
         </p></dd></dl></div></dd><dt id="SQL-CREATETABLE-TABLESPACE"><span class="term"><code class="literal">TABLESPACE <em class="replaceable"><code>tablespace_name</code></em></code></span></dt><dd><p>
      The <em class="replaceable"><code>tablespace_name</code></em> is the name
      of the tablespace in which the new table is to be created.
      If not specified,
      <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a> is consulted, or
      <a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> if the table is temporary.  For
      partitioned tables, since no storage is required for the table itself,
      the tablespace specified overrides <code class="literal">default_tablespace</code>
      as the default tablespace to use for any newly created partitions when no
      other tablespace is explicitly specified.
     </p></dd><dt><span class="term"><code class="literal">USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em></code></span></dt><dd><p>
      This clause allows selection of the tablespace in which the index
      associated with a <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY
      KEY</code>, or <code class="literal">EXCLUDE</code> constraint will be created.
      If not specified,
      <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a> is consulted, or
      <a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> if the table is temporary.
     </p></dd></dl></div><div class="refsect2" id="SQL-CREATETABLE-STORAGE-PARAMETERS"><h3>Storage Parameters</h3><a id="id-1.9.3.85.6.3.2" class="indexterm"></a><p>
    The <code class="literal">WITH</code> clause can specify <em class="firstterm">storage parameters</em>
    for tables, and for indexes associated with a <code class="literal">UNIQUE</code>,
    <code class="literal">PRIMARY KEY</code>, or <code class="literal">EXCLUDE</code> constraint.
    Storage parameters for
    indexes are documented in <a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>.
    The storage parameters currently
    available for tables are listed below.  For many of these parameters, as
    shown, there is an additional parameter with the same name prefixed with
    <code class="literal">toast.</code>, which controls the behavior of the
    table's secondary <acronym class="acronym">TOAST</acronym> table, if any
    (see <a class="xref" href="storage-toast.html" title="73.2. TOAST">Section 73.2</a> for more information about TOAST).
    If a table parameter value is set and the
    equivalent <code class="literal">toast.</code> parameter is not, the TOAST table
    will use the table's parameter value.
    Specifying these parameters for partitioned tables is not supported,
    but you may specify them for individual leaf partitions.
   </p><div class="variablelist"><dl class="variablelist"><dt id="RELOPTION-FILLFACTOR"><span class="term"><code class="varname">fillfactor</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.1.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      The fillfactor for a table is a percentage between 10 and 100.
      100 (complete packing) is the default.  When a smaller fillfactor
      is specified, <code class="command">INSERT</code> operations pack table pages only
      to the indicated percentage; the remaining space on each page is
      reserved for updating rows on that page.  This gives <code class="command">UPDATE</code>
      a chance to place the updated copy of a row on the same page as the
      original, which is more efficient than placing it on a different
      page, and makes <a class="link" href="storage-hot.html" title="73.7. Heap-Only Tuples (HOT)">heap-only tuple
      updates</a> more likely.
      For a table whose entries are never updated, complete packing is the
      best choice, but in heavily updated tables smaller fillfactors are
      appropriate.  This parameter cannot be set for TOAST tables.
     </p></dd><dt id="RELOPTION-TOAST-TUPLE-TARGET"><span class="term"><code class="literal">toast_tuple_target</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.2.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      The toast_tuple_target specifies the minimum tuple length required before
      we try to compress and/or move long column values into TOAST tables, and
      is also the target length we try to reduce the length below once toasting
      begins. This affects columns marked as External (for move),
      Main (for compression), or Extended (for both) and applies only to new
      tuples. There is no effect on existing rows.
      By default this parameter is set to allow at least 4 tuples per block,
      which with the default block size will be 2040 bytes. Valid values are
      between 128 bytes and the (block size - header), by default 8160 bytes.
      Changing this value may not be useful for very short or very long rows.
      Note that the default setting is often close to optimal, and
      it is possible that setting this parameter could have negative
      effects in some cases.
      This parameter cannot be set for TOAST tables.
     </p></dd><dt id="RELOPTION-PARALLEL-WORKERS"><span class="term"><code class="literal">parallel_workers</code> (<code class="type">integer</code>)
     <a id="id-1.9.3.85.6.3.4.3.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      This sets the number of workers that should be used to assist a parallel
      scan of this table.  If not set, the system will determine a value based
      on the relation size.  The actual number of workers chosen by the planner
      or by utility statements that use parallel scans may be less, for example
      due to the setting of <a class="xref" href="runtime-config-resource.html#GUC-MAX-WORKER-PROCESSES">max_worker_processes</a>.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-ENABLED"><span class="term"><code class="literal">autovacuum_enabled</code>, <code class="literal">toast.autovacuum_enabled</code> (<code class="type">boolean</code>)
    <a id="id-1.9.3.85.6.3.4.4.1.4" class="indexterm"></a>
    </span></dt><dd><p>
     Enables or disables the autovacuum daemon for a particular table.
     If true, the autovacuum daemon will perform automatic <code class="command">VACUUM</code>
     and/or <code class="command">ANALYZE</code> operations on this table following the rules
     discussed in <a class="xref" href="routine-vacuuming.html#AUTOVACUUM" title="25.1.6. The Autovacuum Daemon">Section 25.1.6</a>.
     If false, this table will not be autovacuumed, except to prevent
     transaction ID wraparound. See <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="25.1.5. Preventing Transaction ID Wraparound Failures">Section 25.1.5</a> for
     more about wraparound prevention.
     Note that the autovacuum daemon does not run at all (except to prevent
     transaction ID wraparound) if the <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM">autovacuum</a>
     parameter is false; setting individual tables' storage parameters does
     not override that.  Therefore there is seldom much point in explicitly
     setting this storage parameter to <code class="literal">true</code>, only
     to <code class="literal">false</code>.
     </p></dd><dt id="RELOPTION-VACUUM-INDEX-CLEANUP"><span class="term"><code class="literal">vacuum_index_cleanup</code>, <code class="literal">toast.vacuum_index_cleanup</code> (<code class="type">enum</code>)
    <a id="id-1.9.3.85.6.3.4.5.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Forces or disables index cleanup when <code class="command">VACUUM</code>
      is run on this table.  The default value is
      <code class="literal">AUTO</code>.  With <code class="literal">OFF</code>, index
      cleanup is disabled, with <code class="literal">ON</code> it is enabled,
      and with <code class="literal">AUTO</code> a decision is made dynamically,
      each time <code class="command">VACUUM</code> runs.  The dynamic behavior
      allows <code class="command">VACUUM</code> to avoid needlessly scanning
      indexes to remove very few dead tuples.  Forcibly disabling all
      index cleanup can speed up <code class="command">VACUUM</code> very
      significantly, but may also lead to severely bloated indexes if
      table modifications are frequent.  The
      <code class="literal">INDEX_CLEANUP</code> parameter of <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>, if
      specified, overrides the value of this option.
     </p></dd><dt id="RELOPTION-VACUUM-TRUNCATE"><span class="term"><code class="literal">vacuum_truncate</code>, <code class="literal">toast.vacuum_truncate</code> (<code class="type">boolean</code>)
    <a id="id-1.9.3.85.6.3.4.6.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Enables or disables vacuum to try to truncate off any empty pages
      at the end of this table. The default value is <code class="literal">true</code>.
      If <code class="literal">true</code>, <code class="command">VACUUM</code> and
      autovacuum do the truncation and the disk space for
      the truncated pages is returned to the operating system.
      Note that the truncation requires <code class="literal">ACCESS EXCLUSIVE</code>
      lock on the table. The <code class="literal">TRUNCATE</code> parameter
      of <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>, if specified, overrides the value
      of this option.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-THRESHOLD"><span class="term"><code class="literal">autovacuum_vacuum_threshold</code>, <code class="literal">toast.autovacuum_vacuum_threshold</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.7.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-THRESHOLD">autovacuum_vacuum_threshold</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-SCALE-FACTOR"><span class="term"><code class="literal">autovacuum_vacuum_scale_factor</code>, <code class="literal">toast.autovacuum_vacuum_scale_factor</code> (<code class="type">floating point</code>)
    <a id="id-1.9.3.85.6.3.4.8.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-SCALE-FACTOR">autovacuum_vacuum_scale_factor</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-INSERT-THRESHOLD"><span class="term"><code class="literal">autovacuum_vacuum_insert_threshold</code>, <code class="literal">toast.autovacuum_vacuum_insert_threshold</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.9.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-INSERT-THRESHOLD">autovacuum_vacuum_insert_threshold</a>
      parameter.  The special value of -1 may be used to disable insert vacuums on the table.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-INSERT-SCALE-FACTOR"><span class="term"><code class="literal">autovacuum_vacuum_insert_scale_factor</code>, <code class="literal">toast.autovacuum_vacuum_insert_scale_factor</code> (<code class="type">floating point</code>)
    <a id="id-1.9.3.85.6.3.4.10.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-INSERT-SCALE-FACTOR">autovacuum_vacuum_insert_scale_factor</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-ANALYZE-THRESHOLD"><span class="term"><code class="literal">autovacuum_analyze_threshold</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.11.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-ANALYZE-THRESHOLD">autovacuum_analyze_threshold</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-ANALYZE-SCALE-FACTOR"><span class="term"><code class="literal">autovacuum_analyze_scale_factor</code> (<code class="type">floating point</code>)
    <a id="id-1.9.3.85.6.3.4.12.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-ANALYZE-SCALE-FACTOR">autovacuum_analyze_scale_factor</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-COST-DELAY"><span class="term"><code class="literal">autovacuum_vacuum_cost_delay</code>, <code class="literal">toast.autovacuum_vacuum_cost_delay</code> (<code class="type">floating point</code>)
    <a id="id-1.9.3.85.6.3.4.13.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-COST-DELAY">autovacuum_vacuum_cost_delay</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-VACUUM-COST-LIMIT"><span class="term"><code class="literal">autovacuum_vacuum_cost_limit</code>, <code class="literal">toast.autovacuum_vacuum_cost_limit</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.14.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-COST-LIMIT">autovacuum_vacuum_cost_limit</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-FREEZE-MIN-AGE"><span class="term"><code class="literal">autovacuum_freeze_min_age</code>, <code class="literal">toast.autovacuum_freeze_min_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.15.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-MIN-AGE">vacuum_freeze_min_age</a>
      parameter.  Note that autovacuum will ignore
      per-table <code class="literal">autovacuum_freeze_min_age</code> parameters that are
      larger than half the
      system-wide <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a> setting.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-FREEZE-MAX-AGE"><span class="term"><code class="literal">autovacuum_freeze_max_age</code>, <code class="literal">toast.autovacuum_freeze_max_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.16.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a>
      parameter.  Note that autovacuum will ignore
      per-table <code class="literal">autovacuum_freeze_max_age</code> parameters that are
      larger than the system-wide setting (it can only be set smaller).
     </p></dd><dt id="RELOPTION-AUTOVACUUM-FREEZE-TABLE-AGE"><span class="term"><code class="literal">autovacuum_freeze_table_age</code>, <code class="literal">toast.autovacuum_freeze_table_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.17.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-TABLE-AGE">vacuum_freeze_table_age</a>
      parameter.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-MIN-AGE"><span class="term"><code class="literal">autovacuum_multixact_freeze_min_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_min_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.18.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-MULTIXACT-FREEZE-MIN-AGE">vacuum_multixact_freeze_min_age</a>
      parameter.  Note that autovacuum will ignore
      per-table <code class="literal">autovacuum_multixact_freeze_min_age</code> parameters
      that are larger than half the
      system-wide <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a>
      setting.
     </p></dd><dt id="RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE"><span class="term"><code class="literal">autovacuum_multixact_freeze_max_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_max_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.19.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value
      for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a> parameter.
      Note that autovacuum will ignore
      per-table <code class="literal">autovacuum_multixact_freeze_max_age</code> parameters
      that are larger than the system-wide setting (it can only be set
      smaller).
     </p></dd><dt id="RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-TABLE-AGE"><span class="term"><code class="literal">autovacuum_multixact_freeze_table_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_table_age</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.20.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value
      for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-MULTIXACT-FREEZE-TABLE-AGE">vacuum_multixact_freeze_table_age</a> parameter.
     </p></dd><dt id="RELOPTION-LOG-AUTOVACUUM-MIN-DURATION"><span class="term"><code class="literal">log_autovacuum_min_duration</code>, <code class="literal">toast.log_autovacuum_min_duration</code> (<code class="type">integer</code>)
    <a id="id-1.9.3.85.6.3.4.21.1.4" class="indexterm"></a>
    </span></dt><dd><p>
      Per-table value for <a class="xref" href="runtime-config-logging.html#GUC-LOG-AUTOVACUUM-MIN-DURATION">log_autovacuum_min_duration</a>
      parameter.
     </p></dd><dt id="RELOPTION-USER-CATALOG-TABLE"><span class="term"><code class="literal">user_catalog_table</code> (<code class="type">boolean</code>)
    <a id="id-1.9.3.85.6.3.4.22.1.3" class="indexterm"></a>
    </span></dt><dd><p>
      Declare the table as an additional catalog table for purposes of
      logical replication. See
      <a class="xref" href="logicaldecoding-output-plugin.html#LOGICALDECODING-CAPABILITIES" title="49.6.2. Capabilities">Section 49.6.2</a> for details.
      This parameter cannot be set for TOAST tables.
     </p></dd></dl></div></div></div><div class="refsect1" id="SQL-CREATETABLE-NOTES"><h2>Notes</h2><p>
     <span class="productname">PostgreSQL</span> automatically creates an
     index for each unique constraint and primary key constraint to
     enforce uniqueness.  Thus, it is not necessary to create an
     index explicitly for primary key columns.  (See <a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a> for more information.)
    </p><p>
     Unique constraints and primary keys are not inherited in the
     current implementation.  This makes the combination of
     inheritance and unique constraints rather dysfunctional.
    </p><p>
     A table cannot have more than 1600 columns.  (In practice, the
     effective limit is usually lower because of tuple-length constraints.)
    </p></div><div class="refsect1" id="SQL-CREATETABLE-EXAMPLES"><h2>Examples</h2><p>
   Create table <code class="structname">films</code> and table
   <code class="structname">distributors</code>:

</p><pre class="programlisting">
CREATE TABLE films (
    code        char(5) CONSTRAINT firstkey PRIMARY KEY,
    title       varchar(40) NOT NULL,
    did         integer NOT NULL,
    date_prod   date,
    kind        varchar(10),
    len         interval hour to minute
);

CREATE TABLE distributors (
     did    integer PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
     name   varchar(40) NOT NULL CHECK (name &lt;&gt; '')
);
</pre><p>
  </p><p>
   Create a table with a 2-dimensional array:

</p><pre class="programlisting">
CREATE TABLE array_int (
    vector  int[][]
);
</pre><p>
  </p><p>
   Define a unique table constraint for the table
   <code class="literal">films</code>.  Unique table constraints can be defined
   on one or more columns of the table:

</p><pre class="programlisting">
CREATE TABLE films (
    code        char(5),
    title       varchar(40),
    did         integer,
    date_prod   date,
    kind        varchar(10),
    len         interval hour to minute,
    CONSTRAINT production UNIQUE(date_prod)
);
</pre><p>
  </p><p>
   Define a check column constraint:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer CHECK (did &gt; 100),
    name    varchar(40)
);
</pre><p>
  </p><p>
   Define a check table constraint:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer,
    name    varchar(40),
    CONSTRAINT con1 CHECK (did &gt; 100 AND name &lt;&gt; '')
);
</pre><p>
  </p><p>
   Define a primary key table constraint for the table
   <code class="structname">films</code>:

</p><pre class="programlisting">
CREATE TABLE films (
    code        char(5),
    title       varchar(40),
    did         integer,
    date_prod   date,
    kind        varchar(10),
    len         interval hour to minute,
    CONSTRAINT code_title PRIMARY KEY(code,title)
);
</pre><p>
  </p><p>
   Define a primary key constraint for table
   <code class="structname">distributors</code>.  The following two examples are
   equivalent, the first using the table constraint syntax, the second
   the column constraint syntax:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer,
    name    varchar(40),
    PRIMARY KEY(did)
);

CREATE TABLE distributors (
    did     integer PRIMARY KEY,
    name    varchar(40)
);
</pre><p>
  </p><p>
   Assign a literal constant default value for the column
   <code class="literal">name</code>, arrange for the default value of column
   <code class="literal">did</code> to be generated by selecting the next value
   of a sequence object, and make the default value of
   <code class="literal">modtime</code> be the time at which the row is
   inserted:

</p><pre class="programlisting">
CREATE TABLE distributors (
    name      varchar(40) DEFAULT 'Luso Films',
    did       integer DEFAULT nextval('distributors_serial'),
    modtime   timestamp DEFAULT current_timestamp
);
</pre><p>
  </p><p>
   Define two <code class="literal">NOT NULL</code> column constraints on the table
   <code class="classname">distributors</code>, one of which is explicitly
   given a name:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer CONSTRAINT no_null NOT NULL,
    name    varchar(40) NOT NULL
);
</pre><p>
    </p><p>
     Define a unique constraint for the <code class="literal">name</code> column:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer,
    name    varchar(40) UNIQUE
);
</pre><p>

     The same, specified as a table constraint:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer,
    name    varchar(40),
    UNIQUE(name)
);
</pre><p>
  </p><p>
   Create the same table, specifying 70% fill factor for both the table
   and its unique index:

</p><pre class="programlisting">
CREATE TABLE distributors (
    did     integer,
    name    varchar(40),
    UNIQUE(name) WITH (fillfactor=70)
)
WITH (fillfactor=70);
</pre><p>
  </p><p>
   Create table <code class="structname">circles</code> with an exclusion
   constraint that prevents any two circles from overlapping:

</p><pre class="programlisting">
CREATE TABLE circles (
    c circle,
    EXCLUDE USING gist (c WITH &amp;&amp;)
);
</pre><p>
  </p><p>
   Create table <code class="structname">cinemas</code> in tablespace <code class="structname">diskvol1</code>:

</p><pre class="programlisting">
CREATE TABLE cinemas (
        id serial,
        name text,
        location text
) TABLESPACE diskvol1;
</pre><p>
  </p><p>
   Create a composite type and a typed table:
</p><pre class="programlisting">
CREATE TYPE employee_type AS (name text, salary numeric);

CREATE TABLE employees OF employee_type (
    PRIMARY KEY (name),
    salary WITH OPTIONS DEFAULT 1000
);
</pre><p>
   Create a range partitioned table:
</p><pre class="programlisting">
CREATE TABLE measurement (
    logdate         date not null,
    peaktemp        int,
    unitsales       int
) PARTITION BY RANGE (logdate);
</pre><p>
   Create a range partitioned table with multiple columns in the partition key:
</p><pre class="programlisting">
CREATE TABLE measurement_year_month (
    logdate         date not null,
    peaktemp        int,
    unitsales       int
) PARTITION BY RANGE (EXTRACT(YEAR FROM logdate), EXTRACT(MONTH FROM logdate));
</pre><p>
   Create a list partitioned table:
</p><pre class="programlisting">
CREATE TABLE cities (
    city_id      bigserial not null,
    name         text not null,
    population   bigint
) PARTITION BY LIST (left(lower(name), 1));
</pre><p>
   Create a hash partitioned table:
</p><pre class="programlisting">
CREATE TABLE orders (
    order_id     bigint not null,
    cust_id      bigint not null,
    status       text
) PARTITION BY HASH (order_id);
</pre><p>
   Create partition of a range partitioned table:
</p><pre class="programlisting">
CREATE TABLE measurement_y2016m07
    PARTITION OF measurement (
    unitsales DEFAULT 0
) FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
</pre><p>
   Create a few partitions of a range partitioned table with multiple
   columns in the partition key:
</p><pre class="programlisting">
CREATE TABLE measurement_ym_older
    PARTITION OF measurement_year_month
    FOR VALUES FROM (MINVALUE, MINVALUE) TO (2016, 11);

CREATE TABLE measurement_ym_y2016m11
    PARTITION OF measurement_year_month
    FOR VALUES FROM (2016, 11) TO (2016, 12);

CREATE TABLE measurement_ym_y2016m12
    PARTITION OF measurement_year_month
    FOR VALUES FROM (2016, 12) TO (2017, 01);

CREATE TABLE measurement_ym_y2017m01
    PARTITION OF measurement_year_month
    FOR VALUES FROM (2017, 01) TO (2017, 02);
</pre><p>
   Create partition of a list partitioned table:
</p><pre class="programlisting">
CREATE TABLE cities_ab
    PARTITION OF cities (
    CONSTRAINT city_id_nonzero CHECK (city_id != 0)
) FOR VALUES IN ('a', 'b');
</pre><p>
   Create partition of a list partitioned table that is itself further
   partitioned and then add a partition to it:
</p><pre class="programlisting">
CREATE TABLE cities_ab
    PARTITION OF cities (
    CONSTRAINT city_id_nonzero CHECK (city_id != 0)
) FOR VALUES IN ('a', 'b') PARTITION BY RANGE (population);

CREATE TABLE cities_ab_10000_to_100000
    PARTITION OF cities_ab FOR VALUES FROM (10000) TO (100000);
</pre><p>
   Create partitions of a hash partitioned table:
</p><pre class="programlisting">
CREATE TABLE orders_p1 PARTITION OF orders
    FOR VALUES WITH (MODULUS 4, REMAINDER 0);
CREATE TABLE orders_p2 PARTITION OF orders
    FOR VALUES WITH (MODULUS 4, REMAINDER 1);
CREATE TABLE orders_p3 PARTITION OF orders
    FOR VALUES WITH (MODULUS 4, REMAINDER 2);
CREATE TABLE orders_p4 PARTITION OF orders
    FOR VALUES WITH (MODULUS 4, REMAINDER 3);
</pre><p>
   Create a default partition:
</p><pre class="programlisting">
CREATE TABLE cities_partdef
    PARTITION OF cities DEFAULT;
</pre></div><div class="refsect1" id="SQL-CREATETABLE-COMPATIBILITY"><h2>Compatibility</h2><p>
   The <code class="command">CREATE TABLE</code> command conforms to the
   <acronym class="acronym">SQL</acronym> standard, with exceptions listed below.
  </p><div class="refsect2" id="id-1.9.3.85.9.3"><h3>Temporary Tables</h3><p>
    Although the syntax of <code class="literal">CREATE TEMPORARY TABLE</code>
    resembles that of the SQL standard, the effect is not the same.  In the
    standard,
    temporary tables are defined just once and automatically exist (starting
    with empty contents) in every session that needs them.
    <span class="productname">PostgreSQL</span> instead
    requires each session to issue its own <code class="literal">CREATE TEMPORARY
    TABLE</code> command for each temporary table to be used.  This allows
    different sessions to use the same temporary table name for different
    purposes, whereas the standard's approach constrains all instances of a
    given temporary table name to have the same table structure.
   </p><p>
    The standard's definition of the behavior of temporary tables is
    widely ignored.  <span class="productname">PostgreSQL</span>'s behavior
    on this point is similar to that of several other SQL databases.
   </p><p>
    The SQL standard also distinguishes between global and local temporary
    tables, where a local temporary table has a separate set of contents for
    each SQL module within each session, though its definition is still shared
    across sessions.  Since <span class="productname">PostgreSQL</span> does not
    support SQL modules, this distinction is not relevant in
    <span class="productname">PostgreSQL</span>.
   </p><p>
    For compatibility's sake, <span class="productname">PostgreSQL</span> will
    accept the <code class="literal">GLOBAL</code> and <code class="literal">LOCAL</code> keywords
    in a temporary table declaration, but they currently have no effect.
    Use of these keywords is discouraged, since future versions of
    <span class="productname">PostgreSQL</span> might adopt a more
    standard-compliant interpretation of their meaning.
   </p><p>
    The <code class="literal">ON COMMIT</code> clause for temporary tables
    also resembles the SQL standard, but has some differences.
    If the <code class="literal">ON COMMIT</code> clause is omitted, SQL specifies that the
    default behavior is <code class="literal">ON COMMIT DELETE ROWS</code>.  However, the
    default behavior in <span class="productname">PostgreSQL</span> is
    <code class="literal">ON COMMIT PRESERVE ROWS</code>.  The <code class="literal">ON COMMIT
    DROP</code> option does not exist in SQL.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.4"><h3>Non-Deferred Uniqueness Constraints</h3><p>
    When a <code class="literal">UNIQUE</code> or <code class="literal">PRIMARY KEY</code> constraint is
    not deferrable, <span class="productname">PostgreSQL</span> checks for
    uniqueness immediately whenever a row is inserted or modified.
    The SQL standard says that uniqueness should be enforced only at
    the end of the statement; this makes a difference when, for example,
    a single command updates multiple key values.  To obtain
    standard-compliant behavior, declare the constraint as
    <code class="literal">DEFERRABLE</code> but not deferred (i.e., <code class="literal">INITIALLY
    IMMEDIATE</code>).  Be aware that this can be significantly slower than
    immediate uniqueness checking.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.5"><h3>Column Check Constraints</h3><p>
    The SQL standard says that <code class="literal">CHECK</code> column constraints
    can only refer to the column they apply to; only <code class="literal">CHECK</code>
    table constraints can refer to multiple columns.
    <span class="productname">PostgreSQL</span> does not enforce this
    restriction; it treats column and table check constraints alike.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.6"><h3><code class="literal">EXCLUDE</code> Constraint</h3><p>
    The <code class="literal">EXCLUDE</code> constraint type is a
    <span class="productname">PostgreSQL</span> extension.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.7"><h3>Foreign-Key Constraint Actions</h3><p>
    The ability to specify column lists in the foreign-key actions
    <code class="literal">SET DEFAULT</code> and <code class="literal">SET NULL</code> is a
    <span class="productname">PostgreSQL</span> extension.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.8"><h3><code class="literal">NULL</code> <span class="quote"><span class="quote">Constraint</span></span></h3><p>
    The <code class="literal">NULL</code> <span class="quote"><span class="quote">constraint</span></span> (actually a
    non-constraint) is a <span class="productname">PostgreSQL</span>
    extension to the SQL standard that is included for compatibility with some
    other database systems (and for symmetry with the <code class="literal">NOT
    NULL</code> constraint).  Since it is the default for any
    column, its presence is simply noise.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.9"><h3>Constraint Naming</h3><p>
    The SQL standard says that table and domain constraints must have names
    that are unique across the schema containing the table or domain.
    <span class="productname">PostgreSQL</span> is laxer: it only requires
    constraint names to be unique across the constraints attached to a
    particular table or domain.  However, this extra freedom does not exist
    for index-based constraints (<code class="literal">UNIQUE</code>,
    <code class="literal">PRIMARY KEY</code>, and <code class="literal">EXCLUDE</code>
    constraints), because the associated index is named the same as the
    constraint, and index names must be unique across all relations within
    the same schema.
   </p><p>
    Currently, <span class="productname">PostgreSQL</span> does not record names
    for <code class="literal">NOT NULL</code> constraints at all, so they are not
    subject to the uniqueness restriction.  This might change in a future
    release.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.10"><h3>Inheritance</h3><p>
    Multiple inheritance via the <code class="literal">INHERITS</code> clause is
    a <span class="productname">PostgreSQL</span> language extension.
    SQL:1999 and later define single inheritance using a
    different syntax and different semantics.  SQL:1999-style
    inheritance is not yet supported by
    <span class="productname">PostgreSQL</span>.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.11"><h3>Zero-Column Tables</h3><p>
    <span class="productname">PostgreSQL</span> allows a table of no columns
    to be created (for example, <code class="literal">CREATE TABLE foo();</code>).  This
    is an extension from the SQL standard, which does not allow zero-column
    tables.  Zero-column tables are not in themselves very useful, but
    disallowing them creates odd special cases for <code class="command">ALTER TABLE
    DROP COLUMN</code>, so it seems cleaner to ignore this spec restriction.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.12"><h3>Multiple Identity Columns</h3><p>
    <span class="productname">PostgreSQL</span> allows a table to have more than one
    identity column.  The standard specifies that a table can have at most one
    identity column.  This is relaxed mainly to give more flexibility for
    doing schema changes or migrations.  Note that
    the <code class="command">INSERT</code> command supports only one override clause
    that applies to the entire statement, so having multiple identity columns
    with different behaviors is not well supported.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.13"><h3>Generated Columns</h3><p>
    The option <code class="literal">STORED</code> is not standard but is also used by
    other SQL implementations.  The SQL standard does not specify the storage
    of generated columns.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.14"><h3><code class="literal">LIKE</code> Clause</h3><p>
    While a <code class="literal">LIKE</code> clause exists in the SQL standard, many of the
    options that <span class="productname">PostgreSQL</span> accepts for it are not
    in the standard, and some of the standard's options are not implemented
    by <span class="productname">PostgreSQL</span>.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.15"><h3><code class="literal">WITH</code> Clause</h3><p>
    The <code class="literal">WITH</code> clause is a <span class="productname">PostgreSQL</span>
    extension; storage parameters are not in the standard.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.16"><h3>Tablespaces</h3><p>
    The <span class="productname">PostgreSQL</span> concept of tablespaces is not
    part of the standard.  Hence, the clauses <code class="literal">TABLESPACE</code>
    and <code class="literal">USING INDEX TABLESPACE</code> are extensions.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.17"><h3>Typed Tables</h3><p>
    Typed tables implement a subset of the SQL standard.  According to
    the standard, a typed table has columns corresponding to the
    underlying composite type as well as one other column that is
    the <span class="quote"><span class="quote">self-referencing column</span></span>.
    <span class="productname">PostgreSQL</span> does not support self-referencing
    columns explicitly.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.18"><h3><code class="literal">PARTITION BY</code> Clause</h3><p>
    The <code class="literal">PARTITION BY</code> clause is a
    <span class="productname">PostgreSQL</span> extension.
   </p></div><div class="refsect2" id="id-1.9.3.85.9.19"><h3><code class="literal">PARTITION OF</code> Clause</h3><p>
    The <code class="literal">PARTITION OF</code> clause is a
    <span class="productname">PostgreSQL</span> extension.
   </p></div></div><div class="refsect1" id="id-1.9.3.85.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-altertable.html" title="ALTER TABLE"><span class="refentrytitle">ALTER TABLE</span></a>, <a class="xref" href="sql-droptable.html" title="DROP TABLE"><span class="refentrytitle">DROP TABLE</span></a>, <a class="xref" href="sql-createtableas.html" title="CREATE TABLE AS"><span class="refentrytitle">CREATE TABLE AS</span></a>, <a class="xref" href="sql-createtablespace.html" title="CREATE TABLESPACE"><span class="refentrytitle">CREATE TABLESPACE</span></a>, <a class="xref" href="sql-createtype.html" title="CREATE TYPE"><span class="refentrytitle">CREATE TYPE</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-createtableas.html" title="CREATE TABLE AS">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE SUBSCRIPTION </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> CREATE TABLE AS</td></tr></table></div></body></html>