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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 16.2 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> [ STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT } ] [ 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> <a href="#SQL-CREATETABLE-TEMPORARY" class="id_link">#</a></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> <a href="#SQL-CREATETABLE-UNLOGGED" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-IF-NOT-EXISTS"><span class="term"><code class="literal">IF NOT EXISTS</code></span> <a href="#SQL-CREATETABLE-PARMS-IF-NOT-EXISTS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-TABLE-NAME"><span class="term"><em class="replaceable"><code>table_name</code></em></span> <a href="#SQL-CREATETABLE-PARMS-TABLE-NAME" class="id_link">#</a></dt><dd><p> + The name (optionally schema-qualified) of the table to be created. + </p></dd><dt id="SQL-CREATETABLE-PARMS-TYPE-NAME"><span class="term"><code class="literal">OF <em class="replaceable"><code>type_name</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-TYPE-NAME" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-COLUMN-NAME"><span class="term"><em class="replaceable"><code>column_name</code></em></span> <a href="#SQL-CREATETABLE-PARMS-COLUMN-NAME" class="id_link">#</a></dt><dd><p> + The name of a column to be created in the new table. + </p></dd><dt id="SQL-CREATETABLE-PARMS-DATA-TYPE"><span class="term"><em class="replaceable"><code>data_type</code></em></span> <a href="#SQL-CREATETABLE-PARMS-DATA-TYPE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-COLLATE"><span class="term"><code class="literal">COLLATE <em class="replaceable"><code>collation</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-COLLATE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-STORAGE"><span class="term"> + <code class="literal">STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT }</code> + <a id="id-1.9.3.85.6.2.9.1.2" class="indexterm"></a> + </span> <a href="#SQL-CREATETABLE-PARMS-STORAGE" class="id_link">#</a></dt><dd><p> + This form sets the storage mode for the column. This controls whether this + column is held inline or in a secondary <acronym class="acronym">TOAST</acronym> table, + and whether the data should be compressed or not. <code class="literal">PLAIN</code> + must be used for fixed-length values such as <code class="type">integer</code> and is + inline, uncompressed. <code class="literal">MAIN</code> is for inline, compressible + data. <code class="literal">EXTERNAL</code> is for external, uncompressed data, and + <code class="literal">EXTENDED</code> is for external, compressed data. + Writing <code class="literal">DEFAULT</code> sets the storage mode to the default + mode for the column's data type. <code class="literal">EXTENDED</code> is the + default for most data types that support non-<code class="literal">PLAIN</code> + storage. + Use of <code class="literal">EXTERNAL</code> will make substring operations on + very large <code class="type">text</code> and <code class="type">bytea</code> values run faster, + at the penalty of increased storage space. + See <a class="xref" href="storage-toast.html" title="73.2. TOAST">Section 73.2</a> for more information. + </p></dd><dt id="SQL-CREATETABLE-PARMS-COMPRESSION"><span class="term"><code class="literal">COMPRESSION <em class="replaceable"><code>compression_method</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-COMPRESSION" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-INHERITS"><span class="term"><code class="literal">INHERITS ( <em class="replaceable"><code>parent_table</code></em> [, ... ] )</code></span> <a href="#SQL-CREATETABLE-PARMS-INHERITS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-PARTITION-BY"><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> <a href="#SQL-CREATETABLE-PARMS-PARTITION-BY" class="id_link">#</a></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> <a href="#SQL-CREATETABLE-PARTITION" class="id_link">#</a></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>=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<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 id="SQL-CREATETABLE-PARMS-LIKE"><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> <a href="#SQL-CREATETABLE-PARMS-LIKE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-COMMENTS"><span class="term"><code class="literal">INCLUDING COMMENTS</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-COMMENTS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-COMPRESSION"><span class="term"><code class="literal">INCLUDING COMPRESSION</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-COMPRESSION" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-CONSTRAINTS"><span class="term"><code class="literal">INCLUDING CONSTRAINTS</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-CONSTRAINTS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-DEFAULTS"><span class="term"><code class="literal">INCLUDING DEFAULTS</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-DEFAULTS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-GENERATED"><span class="term"><code class="literal">INCLUDING GENERATED</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-GENERATED" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-IDENTITY"><span class="term"><code class="literal">INCLUDING IDENTITY</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-IDENTITY" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-INDEXES"><span class="term"><code class="literal">INCLUDING INDEXES</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-INDEXES" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-STATISTICS"><span class="term"><code class="literal">INCLUDING STATISTICS</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-STATISTICS" class="id_link">#</a></dt><dd><p> + Extended statistics are copied to the new table. + </p></dd><dt id="SQL-CREATETABLE-PARMS-LIKE-OPT-STORAGE"><span class="term"><code class="literal">INCLUDING STORAGE</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-STORAGE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-LIKE-OPT-ALL"><span class="term"><code class="literal">INCLUDING ALL</code></span> <a href="#SQL-CREATETABLE-PARMS-LIKE-OPT-ALL" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-CONSTRAINT"><span class="term"><code class="literal">CONSTRAINT <em class="replaceable"><code>constraint_name</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-CONSTRAINT" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-NOT-NULL"><span class="term"><code class="literal">NOT NULL</code></span> <a href="#SQL-CREATETABLE-PARMS-NOT-NULL" class="id_link">#</a></dt><dd><p> + The column is not allowed to contain null values. + </p></dd><dt id="SQL-CREATETABLE-PARMS-NULL"><span class="term"><code class="literal">NULL</code></span> <a href="#SQL-CREATETABLE-PARMS-NULL" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-CHECK"><span class="term"><code class="literal">CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] </code></span> <a href="#SQL-CREATETABLE-PARMS-CHECK" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-DEFAULT"><span class="term"><code class="literal">DEFAULT + <em class="replaceable"><code>default_expr</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-DEFAULT" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-GENERATED-STORED"><span class="term"><code class="literal">GENERATED ALWAYS AS ( <em class="replaceable"><code>generation_expr</code></em> ) STORED</code><a id="id-1.9.3.85.6.2.20.1.2" class="indexterm"></a></span> <a href="#SQL-CREATETABLE-PARMS-GENERATED-STORED" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-GENERATED-IDENTITY"><span class="term"><code class="literal">GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ]</code></span> <a href="#SQL-CREATETABLE-PARMS-GENERATED-IDENTITY" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-UNIQUE"><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> <a href="#SQL-CREATETABLE-PARMS-UNIQUE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-PRIMARY-KEY"><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> <a href="#SQL-CREATETABLE-PARMS-PRIMARY-KEY" class="id_link">#</a></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> <a href="#SQL-CREATETABLE-EXCLUDE" class="id_link">#</a></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">&&</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 id="SQL-CREATETABLE-PARMS-REFERENCES"><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> <a href="#SQL-CREATETABLE-PARMS-REFERENCES" class="id_link">#</a></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. Otherwise, the <em class="replaceable"><code>refcolumn</code></em> + list must refer to the columns of a non-deferrable unique or primary key + constraint or be the columns of a non-partial unique index. 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 id="SQL-CREATETABLE-PARMS-REFERENCES-REFACT-NO-ACTION"><span class="term"><code class="literal">NO ACTION</code></span> <a href="#SQL-CREATETABLE-PARMS-REFERENCES-REFACT-NO-ACTION" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-REFERENCES-REFACT-RESTRICT"><span class="term"><code class="literal">RESTRICT</code></span> <a href="#SQL-CREATETABLE-PARMS-REFERENCES-REFACT-RESTRICT" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-REFERENCES-REFACT-CASCADE"><span class="term"><code class="literal">CASCADE</code></span> <a href="#SQL-CREATETABLE-PARMS-REFERENCES-REFACT-CASCADE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-REFERENCES-REFACT-SET-NULL"><span class="term"><code class="literal">SET NULL [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]</code></span> <a href="#SQL-CREATETABLE-PARMS-REFERENCES-REFACT-SET-NULL" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-REFERENCES-REFACT-SET-DEFAULT"><span class="term"><code class="literal">SET DEFAULT [ ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]</code></span> <a href="#SQL-CREATETABLE-PARMS-REFERENCES-REFACT-SET-DEFAULT" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-DEFERRABLE"><span class="term"><code class="literal">DEFERRABLE</code><br /></span><span class="term"><code class="literal">NOT DEFERRABLE</code></span> <a href="#SQL-CREATETABLE-PARMS-DEFERRABLE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-INITIALLY"><span class="term"><code class="literal">INITIALLY IMMEDIATE</code><br /></span><span class="term"><code class="literal">INITIALLY DEFERRED</code></span> <a href="#SQL-CREATETABLE-PARMS-INITIALLY" class="id_link">#</a></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> <a href="#SQL-CREATETABLE-METHOD" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-WITH"><span class="term"><code class="literal">WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] )</code></span> <a href="#SQL-CREATETABLE-PARMS-WITH" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-WITHOUT-OIDS"><span class="term"><code class="literal">WITHOUT OIDS</code></span> <a href="#SQL-CREATETABLE-PARMS-WITHOUT-OIDS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-ON-COMMIT"><span class="term"><code class="literal">ON COMMIT</code></span> <a href="#SQL-CREATETABLE-PARMS-ON-COMMIT" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-ON-COMMIT-PRESERVE-ROWS"><span class="term"><code class="literal">PRESERVE ROWS</code></span> <a href="#SQL-CREATETABLE-PARMS-ON-COMMIT-PRESERVE-ROWS" class="id_link">#</a></dt><dd><p> + No special action is taken at the ends of transactions. + This is the default behavior. + </p></dd><dt id="SQL-CREATETABLE-PARMS-ON-COMMIT-DELETE-ROWS"><span class="term"><code class="literal">DELETE ROWS</code></span> <a href="#SQL-CREATETABLE-PARMS-ON-COMMIT-DELETE-ROWS" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-ON-COMMIT-DROP"><span class="term"><code class="literal">DROP</code></span> <a href="#SQL-CREATETABLE-PARMS-ON-COMMIT-DROP" class="id_link">#</a></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> <a href="#SQL-CREATETABLE-TABLESPACE" class="id_link">#</a></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 id="SQL-CREATETABLE-PARMS-USING-INDEX-TABLESPACE"><span class="term"><code class="literal">USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em></code></span> <a href="#SQL-CREATETABLE-PARMS-USING-INDEX-TABLESPACE" class="id_link">#</a></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> <a href="#RELOPTION-FILLFACTOR" class="id_link">#</a></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> <a href="#RELOPTION-TOAST-TUPLE-TARGET" class="id_link">#</a></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> <a href="#RELOPTION-PARALLEL-WORKERS" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-ENABLED" class="id_link">#</a></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> <a href="#RELOPTION-VACUUM-INDEX-CLEANUP" class="id_link">#</a></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> <a href="#RELOPTION-VACUUM-TRUNCATE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-THRESHOLD" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-SCALE-FACTOR" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-INSERT-THRESHOLD" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-INSERT-SCALE-FACTOR" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-ANALYZE-THRESHOLD" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-ANALYZE-SCALE-FACTOR" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-COST-DELAY" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-VACUUM-COST-LIMIT" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-FREEZE-MIN-AGE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-FREEZE-MAX-AGE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-FREEZE-TABLE-AGE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-MIN-AGE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE" class="id_link">#</a></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> <a href="#RELOPTION-AUTOVACUUM-MULTIXACT-FREEZE-TABLE-AGE" class="id_link">#</a></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> <a href="#RELOPTION-LOG-AUTOVACUUM-MIN-DURATION" class="id_link">#</a></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> <a href="#RELOPTION-USER-CATALOG-TABLE" class="id_link">#</a></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 <> '') +); +</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 > 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 > 100 AND name <> '') +); +</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 &&) +); +</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 Constraints</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><p> + It is a <span class="productname">PostgreSQL</span> extension that a + foreign key constraint may reference columns of a unique index instead of + columns of a primary key or unique constraint. + </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 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> CREATE TABLE AS</td></tr></table></div></body></html>
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