summaryrefslogtreecommitdiffstats
path: root/sqlglot/dialects/tsql.py
blob: 69adb456d4bafb583f1c9496347ed7192e9e7507 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
from __future__ import annotations

import datetime
import re
import typing as t

from sqlglot import exp, generator, parser, tokens, transforms
from sqlglot.dialects.dialect import (
    Dialect,
    any_value_to_max_sql,
    max_or_greatest,
    min_or_least,
    move_insert_cte_sql,
    parse_date_delta,
    rename_func,
    timestrtotime_sql,
    ts_or_ds_to_date_sql,
)
from sqlglot.expressions import DataType
from sqlglot.helper import seq_get
from sqlglot.time import format_time
from sqlglot.tokens import TokenType

if t.TYPE_CHECKING:
    from sqlglot._typing import E

FULL_FORMAT_TIME_MAPPING = {
    "weekday": "%A",
    "dw": "%A",
    "w": "%A",
    "month": "%B",
    "mm": "%B",
    "m": "%B",
}

DATE_DELTA_INTERVAL = {
    "year": "year",
    "yyyy": "year",
    "yy": "year",
    "quarter": "quarter",
    "qq": "quarter",
    "q": "quarter",
    "month": "month",
    "mm": "month",
    "m": "month",
    "week": "week",
    "ww": "week",
    "wk": "week",
    "day": "day",
    "dd": "day",
    "d": "day",
}


DATE_FMT_RE = re.compile("([dD]{1,2})|([mM]{1,2})|([yY]{1,4})|([hH]{1,2})|([sS]{1,2})")

# N = Numeric, C=Currency
TRANSPILE_SAFE_NUMBER_FMT = {"N", "C"}

DEFAULT_START_DATE = datetime.date(1900, 1, 1)

BIT_TYPES = {exp.EQ, exp.NEQ, exp.Is, exp.In, exp.Select, exp.Alias}


def _format_time_lambda(
    exp_class: t.Type[E], full_format_mapping: t.Optional[bool] = None
) -> t.Callable[[t.List], E]:
    def _format_time(args: t.List) -> E:
        assert len(args) == 2

        return exp_class(
            this=exp.cast(args[1], "datetime"),
            format=exp.Literal.string(
                format_time(
                    args[0].name.lower(),
                    {**TSQL.TIME_MAPPING, **FULL_FORMAT_TIME_MAPPING}
                    if full_format_mapping
                    else TSQL.TIME_MAPPING,
                )
            ),
        )

    return _format_time


def _parse_format(args: t.List) -> exp.Expression:
    this = seq_get(args, 0)
    fmt = seq_get(args, 1)
    culture = seq_get(args, 2)

    number_fmt = fmt and (fmt.name in TRANSPILE_SAFE_NUMBER_FMT or not DATE_FMT_RE.search(fmt.name))

    if number_fmt:
        return exp.NumberToStr(this=this, format=fmt, culture=culture)

    if fmt:
        fmt = exp.Literal.string(
            format_time(fmt.name, TSQL.FORMAT_TIME_MAPPING)
            if len(fmt.name) == 1
            else format_time(fmt.name, TSQL.TIME_MAPPING)
        )

    return exp.TimeToStr(this=this, format=fmt, culture=culture)


def _parse_eomonth(args: t.List) -> exp.Expression:
    date = seq_get(args, 0)
    month_lag = seq_get(args, 1)
    unit = DATE_DELTA_INTERVAL.get("month")

    if month_lag is None:
        return exp.LastDateOfMonth(this=date)

    # Remove month lag argument in parser as its compared with the number of arguments of the resulting class
    args.remove(month_lag)

    return exp.LastDateOfMonth(this=exp.DateAdd(this=date, expression=month_lag, unit=unit))


def _parse_hashbytes(args: t.List) -> exp.Expression:
    kind, data = args
    kind = kind.name.upper() if kind.is_string else ""

    if kind == "MD5":
        args.pop(0)
        return exp.MD5(this=data)
    if kind in ("SHA", "SHA1"):
        args.pop(0)
        return exp.SHA(this=data)
    if kind == "SHA2_256":
        return exp.SHA2(this=data, length=exp.Literal.number(256))
    if kind == "SHA2_512":
        return exp.SHA2(this=data, length=exp.Literal.number(512))

    return exp.func("HASHBYTES", *args)


def generate_date_delta_with_unit_sql(
    self: TSQL.Generator, expression: exp.DateAdd | exp.DateDiff
) -> str:
    func = "DATEADD" if isinstance(expression, exp.DateAdd) else "DATEDIFF"
    return self.func(func, expression.text("unit"), expression.expression, expression.this)


def _format_sql(self: TSQL.Generator, expression: exp.NumberToStr | exp.TimeToStr) -> str:
    fmt = (
        expression.args["format"]
        if isinstance(expression, exp.NumberToStr)
        else exp.Literal.string(
            format_time(
                expression.text("format"),
                t.cast(t.Dict[str, str], TSQL.INVERSE_TIME_MAPPING),
            )
        )
    )
    return self.func("FORMAT", expression.this, fmt, expression.args.get("culture"))


def _string_agg_sql(self: TSQL.Generator, expression: exp.GroupConcat) -> str:
    expression = expression.copy()

    this = expression.this
    distinct = expression.find(exp.Distinct)
    if distinct:
        # exp.Distinct can appear below an exp.Order or an exp.GroupConcat expression
        self.unsupported("T-SQL STRING_AGG doesn't support DISTINCT.")
        this = distinct.pop().expressions[0]

    order = ""
    if isinstance(expression.this, exp.Order):
        if expression.this.this:
            this = expression.this.this.pop()
        order = f" WITHIN GROUP ({self.sql(expression.this)[1:]})"  # Order has a leading space

    separator = expression.args.get("separator") or exp.Literal.string(",")
    return f"STRING_AGG({self.format_args(this, separator)}){order}"


def _parse_date_delta(
    exp_class: t.Type[E], unit_mapping: t.Optional[t.Dict[str, str]] = None
) -> t.Callable[[t.List], E]:
    def inner_func(args: t.List) -> E:
        unit = seq_get(args, 0)
        if unit and unit_mapping:
            unit = exp.var(unit_mapping.get(unit.name.lower(), unit.name))

        start_date = seq_get(args, 1)
        if start_date and start_date.is_number:
            # Numeric types are valid DATETIME values
            if start_date.is_int:
                adds = DEFAULT_START_DATE + datetime.timedelta(days=int(start_date.this))
                start_date = exp.Literal.string(adds.strftime("%F"))
            else:
                # We currently don't handle float values, i.e. they're not converted to equivalent DATETIMEs.
                # This is not a problem when generating T-SQL code, it is when transpiling to other dialects.
                return exp_class(this=seq_get(args, 2), expression=start_date, unit=unit)

        return exp_class(
            this=exp.TimeStrToTime(this=seq_get(args, 2)),
            expression=exp.TimeStrToTime(this=start_date),
            unit=unit,
        )

    return inner_func


class TSQL(Dialect):
    RESOLVES_IDENTIFIERS_AS_UPPERCASE = None
    NULL_ORDERING = "nulls_are_small"
    TIME_FORMAT = "'yyyy-mm-dd hh:mm:ss'"
    SUPPORTS_SEMI_ANTI_JOIN = False
    LOG_BASE_FIRST = False

    TIME_MAPPING = {
        "year": "%Y",
        "qq": "%q",
        "q": "%q",
        "quarter": "%q",
        "dayofyear": "%j",
        "day": "%d",
        "dy": "%d",
        "y": "%Y",
        "week": "%W",
        "ww": "%W",
        "wk": "%W",
        "hour": "%h",
        "hh": "%I",
        "minute": "%M",
        "mi": "%M",
        "n": "%M",
        "second": "%S",
        "ss": "%S",
        "s": "%-S",
        "millisecond": "%f",
        "ms": "%f",
        "weekday": "%W",
        "dw": "%W",
        "month": "%m",
        "mm": "%M",
        "m": "%-M",
        "Y": "%Y",
        "YYYY": "%Y",
        "YY": "%y",
        "MMMM": "%B",
        "MMM": "%b",
        "MM": "%m",
        "M": "%-m",
        "dd": "%d",
        "d": "%-d",
        "HH": "%H",
        "H": "%-H",
        "h": "%-I",
        "S": "%f",
        "yyyy": "%Y",
        "yy": "%y",
    }

    CONVERT_FORMAT_MAPPING = {
        "0": "%b %d %Y %-I:%M%p",
        "1": "%m/%d/%y",
        "2": "%y.%m.%d",
        "3": "%d/%m/%y",
        "4": "%d.%m.%y",
        "5": "%d-%m-%y",
        "6": "%d %b %y",
        "7": "%b %d, %y",
        "8": "%H:%M:%S",
        "9": "%b %d %Y %-I:%M:%S:%f%p",
        "10": "mm-dd-yy",
        "11": "yy/mm/dd",
        "12": "yymmdd",
        "13": "%d %b %Y %H:%M:ss:%f",
        "14": "%H:%M:%S:%f",
        "20": "%Y-%m-%d %H:%M:%S",
        "21": "%Y-%m-%d %H:%M:%S.%f",
        "22": "%m/%d/%y %-I:%M:%S %p",
        "23": "%Y-%m-%d",
        "24": "%H:%M:%S",
        "25": "%Y-%m-%d %H:%M:%S.%f",
        "100": "%b %d %Y %-I:%M%p",
        "101": "%m/%d/%Y",
        "102": "%Y.%m.%d",
        "103": "%d/%m/%Y",
        "104": "%d.%m.%Y",
        "105": "%d-%m-%Y",
        "106": "%d %b %Y",
        "107": "%b %d, %Y",
        "108": "%H:%M:%S",
        "109": "%b %d %Y %-I:%M:%S:%f%p",
        "110": "%m-%d-%Y",
        "111": "%Y/%m/%d",
        "112": "%Y%m%d",
        "113": "%d %b %Y %H:%M:%S:%f",
        "114": "%H:%M:%S:%f",
        "120": "%Y-%m-%d %H:%M:%S",
        "121": "%Y-%m-%d %H:%M:%S.%f",
    }

    FORMAT_TIME_MAPPING = {
        "y": "%B %Y",
        "d": "%m/%d/%Y",
        "H": "%-H",
        "h": "%-I",
        "s": "%Y-%m-%d %H:%M:%S",
        "D": "%A,%B,%Y",
        "f": "%A,%B,%Y %-I:%M %p",
        "F": "%A,%B,%Y %-I:%M:%S %p",
        "g": "%m/%d/%Y %-I:%M %p",
        "G": "%m/%d/%Y %-I:%M:%S %p",
        "M": "%B %-d",
        "m": "%B %-d",
        "O": "%Y-%m-%dT%H:%M:%S",
        "u": "%Y-%M-%D %H:%M:%S%z",
        "U": "%A, %B %D, %Y %H:%M:%S%z",
        "T": "%-I:%M:%S %p",
        "t": "%-I:%M",
        "Y": "%a %Y",
    }

    class Tokenizer(tokens.Tokenizer):
        IDENTIFIERS = ['"', ("[", "]")]
        QUOTES = ["'", '"']
        HEX_STRINGS = [("0x", ""), ("0X", "")]

        KEYWORDS = {
            **tokens.Tokenizer.KEYWORDS,
            "DATETIME2": TokenType.DATETIME,
            "DATETIMEOFFSET": TokenType.TIMESTAMPTZ,
            "DECLARE": TokenType.COMMAND,
            "IMAGE": TokenType.IMAGE,
            "MONEY": TokenType.MONEY,
            "NTEXT": TokenType.TEXT,
            "NVARCHAR(MAX)": TokenType.TEXT,
            "PRINT": TokenType.COMMAND,
            "PROC": TokenType.PROCEDURE,
            "REAL": TokenType.FLOAT,
            "ROWVERSION": TokenType.ROWVERSION,
            "SMALLDATETIME": TokenType.DATETIME,
            "SMALLMONEY": TokenType.SMALLMONEY,
            "SQL_VARIANT": TokenType.VARIANT,
            "TOP": TokenType.TOP,
            "UNIQUEIDENTIFIER": TokenType.UNIQUEIDENTIFIER,
            "UPDATE STATISTICS": TokenType.COMMAND,
            "VARCHAR(MAX)": TokenType.TEXT,
            "XML": TokenType.XML,
            "OUTPUT": TokenType.RETURNING,
            "SYSTEM_USER": TokenType.CURRENT_USER,
            "FOR SYSTEM_TIME": TokenType.TIMESTAMP_SNAPSHOT,
        }

    class Parser(parser.Parser):
        SET_REQUIRES_ASSIGNMENT_DELIMITER = False

        FUNCTIONS = {
            **parser.Parser.FUNCTIONS,
            "CHARINDEX": lambda args: exp.StrPosition(
                this=seq_get(args, 1),
                substr=seq_get(args, 0),
                position=seq_get(args, 2),
            ),
            "DATEADD": parse_date_delta(exp.DateAdd, unit_mapping=DATE_DELTA_INTERVAL),
            "DATEDIFF": _parse_date_delta(exp.DateDiff, unit_mapping=DATE_DELTA_INTERVAL),
            "DATENAME": _format_time_lambda(exp.TimeToStr, full_format_mapping=True),
            "DATEPART": _format_time_lambda(exp.TimeToStr),
            "EOMONTH": _parse_eomonth,
            "FORMAT": _parse_format,
            "GETDATE": exp.CurrentTimestamp.from_arg_list,
            "HASHBYTES": _parse_hashbytes,
            "IIF": exp.If.from_arg_list,
            "ISNULL": exp.Coalesce.from_arg_list,
            "JSON_VALUE": exp.JSONExtractScalar.from_arg_list,
            "LEN": exp.Length.from_arg_list,
            "REPLICATE": exp.Repeat.from_arg_list,
            "SQUARE": lambda args: exp.Pow(this=seq_get(args, 0), expression=exp.Literal.number(2)),
            "SYSDATETIME": exp.CurrentTimestamp.from_arg_list,
            "SUSER_NAME": exp.CurrentUser.from_arg_list,
            "SUSER_SNAME": exp.CurrentUser.from_arg_list,
            "SYSTEM_USER": exp.CurrentUser.from_arg_list,
        }

        JOIN_HINTS = {
            "LOOP",
            "HASH",
            "MERGE",
            "REMOTE",
        }

        VAR_LENGTH_DATATYPES = {
            DataType.Type.NVARCHAR,
            DataType.Type.VARCHAR,
            DataType.Type.CHAR,
            DataType.Type.NCHAR,
        }

        RETURNS_TABLE_TOKENS = parser.Parser.ID_VAR_TOKENS - {
            TokenType.TABLE,
            *parser.Parser.TYPE_TOKENS,
        }

        STATEMENT_PARSERS = {
            **parser.Parser.STATEMENT_PARSERS,
            TokenType.END: lambda self: self._parse_command(),
        }

        LOG_DEFAULTS_TO_LN = True

        CONCAT_NULL_OUTPUTS_STRING = True

        ALTER_TABLE_ADD_COLUMN_KEYWORD = False

        def _parse_projections(self) -> t.List[exp.Expression]:
            """
            T-SQL supports the syntax alias = expression in the SELECT's projection list,
            so we transform all parsed Selects to convert their EQ projections into Aliases.

            See: https://learn.microsoft.com/en-us/sql/t-sql/queries/select-clause-transact-sql?view=sql-server-ver16#syntax
            """
            return [
                exp.alias_(projection.expression, projection.this.this, copy=False)
                if isinstance(projection, exp.EQ) and isinstance(projection.this, exp.Column)
                else projection
                for projection in super()._parse_projections()
            ]

        def _parse_commit_or_rollback(self) -> exp.Commit | exp.Rollback:
            """Applies to SQL Server and Azure SQL Database
            COMMIT [ { TRAN | TRANSACTION }
                [ transaction_name | @tran_name_variable ] ]
                [ WITH ( DELAYED_DURABILITY = { OFF | ON } ) ]

            ROLLBACK { TRAN | TRANSACTION }
                [ transaction_name | @tran_name_variable
                | savepoint_name | @savepoint_variable ]
            """
            rollback = self._prev.token_type == TokenType.ROLLBACK

            self._match_texts({"TRAN", "TRANSACTION"})
            this = self._parse_id_var()

            if rollback:
                return self.expression(exp.Rollback, this=this)

            durability = None
            if self._match_pair(TokenType.WITH, TokenType.L_PAREN):
                self._match_text_seq("DELAYED_DURABILITY")
                self._match(TokenType.EQ)

                if self._match_text_seq("OFF"):
                    durability = False
                else:
                    self._match(TokenType.ON)
                    durability = True

                self._match_r_paren()

            return self.expression(exp.Commit, this=this, durability=durability)

        def _parse_transaction(self) -> exp.Transaction | exp.Command:
            """Applies to SQL Server and Azure SQL Database
            BEGIN { TRAN | TRANSACTION }
            [ { transaction_name | @tran_name_variable }
            [ WITH MARK [ 'description' ] ]
            ]
            """
            if self._match_texts(("TRAN", "TRANSACTION")):
                transaction = self.expression(exp.Transaction, this=self._parse_id_var())
                if self._match_text_seq("WITH", "MARK"):
                    transaction.set("mark", self._parse_string())

                return transaction

            return self._parse_as_command(self._prev)

        def _parse_returns(self) -> exp.ReturnsProperty:
            table = self._parse_id_var(any_token=False, tokens=self.RETURNS_TABLE_TOKENS)
            returns = super()._parse_returns()
            returns.set("table", table)
            return returns

        def _parse_convert(
            self, strict: bool, safe: t.Optional[bool] = None
        ) -> t.Optional[exp.Expression]:
            to = self._parse_types()
            self._match(TokenType.COMMA)
            this = self._parse_conjunction()

            if not to or not this:
                return None

            # Retrieve length of datatype and override to default if not specified
            if seq_get(to.expressions, 0) is None and to.this in self.VAR_LENGTH_DATATYPES:
                to = exp.DataType.build(to.this, expressions=[exp.Literal.number(30)], nested=False)

            # Check whether a conversion with format is applicable
            if self._match(TokenType.COMMA):
                format_val = self._parse_number()
                format_val_name = format_val.name if format_val else ""

                if format_val_name not in TSQL.CONVERT_FORMAT_MAPPING:
                    raise ValueError(
                        f"CONVERT function at T-SQL does not support format style {format_val_name}"
                    )

                format_norm = exp.Literal.string(TSQL.CONVERT_FORMAT_MAPPING[format_val_name])

                # Check whether the convert entails a string to date format
                if to.this == DataType.Type.DATE:
                    return self.expression(exp.StrToDate, this=this, format=format_norm)
                # Check whether the convert entails a string to datetime format
                elif to.this == DataType.Type.DATETIME:
                    return self.expression(exp.StrToTime, this=this, format=format_norm)
                # Check whether the convert entails a date to string format
                elif to.this in self.VAR_LENGTH_DATATYPES:
                    return self.expression(
                        exp.Cast if strict else exp.TryCast,
                        to=to,
                        this=self.expression(exp.TimeToStr, this=this, format=format_norm),
                        safe=safe,
                    )
                elif to.this == DataType.Type.TEXT:
                    return self.expression(exp.TimeToStr, this=this, format=format_norm)

            # Entails a simple cast without any format requirement
            return self.expression(exp.Cast if strict else exp.TryCast, this=this, to=to, safe=safe)

        def _parse_user_defined_function(
            self, kind: t.Optional[TokenType] = None
        ) -> t.Optional[exp.Expression]:
            this = super()._parse_user_defined_function(kind=kind)

            if (
                kind == TokenType.FUNCTION
                or isinstance(this, exp.UserDefinedFunction)
                or self._match(TokenType.ALIAS, advance=False)
            ):
                return this

            expressions = self._parse_csv(self._parse_function_parameter)
            return self.expression(exp.UserDefinedFunction, this=this, expressions=expressions)

        def _parse_id_var(
            self,
            any_token: bool = True,
            tokens: t.Optional[t.Collection[TokenType]] = None,
        ) -> t.Optional[exp.Expression]:
            is_temporary = self._match(TokenType.HASH)
            is_global = is_temporary and self._match(TokenType.HASH)

            this = super()._parse_id_var(any_token=any_token, tokens=tokens)
            if this:
                if is_global:
                    this.set("global", True)
                elif is_temporary:
                    this.set("temporary", True)

            return this

        def _parse_create(self) -> exp.Create | exp.Command:
            create = super()._parse_create()

            if isinstance(create, exp.Create):
                table = create.this.this if isinstance(create.this, exp.Schema) else create.this
                if isinstance(table, exp.Table) and table.this.args.get("temporary"):
                    if not create.args.get("properties"):
                        create.set("properties", exp.Properties(expressions=[]))

                    create.args["properties"].append("expressions", exp.TemporaryProperty())

            return create

        def _parse_if(self) -> t.Optional[exp.Expression]:
            index = self._index

            if self._match_text_seq("OBJECT_ID"):
                self._parse_wrapped_csv(self._parse_string)
                if self._match_text_seq("IS", "NOT", "NULL") and self._match(TokenType.DROP):
                    return self._parse_drop(exists=True)
                self._retreat(index)

            return super()._parse_if()

        def _parse_unique(self) -> exp.UniqueColumnConstraint:
            return self.expression(
                exp.UniqueColumnConstraint,
                this=None
                if self._curr and self._curr.text.upper() in {"CLUSTERED", "NONCLUSTERED"}
                else self._parse_schema(self._parse_id_var(any_token=False)),
            )

    class Generator(generator.Generator):
        LIMIT_IS_TOP = True
        QUERY_HINTS = False
        RETURNING_END = False
        NVL2_SUPPORTED = False
        ALTER_TABLE_ADD_COLUMN_KEYWORD = False
        LIMIT_FETCH = "FETCH"
        COMPUTED_COLUMN_WITH_TYPE = False

        TYPE_MAPPING = {
            **generator.Generator.TYPE_MAPPING,
            exp.DataType.Type.BOOLEAN: "BIT",
            exp.DataType.Type.DECIMAL: "NUMERIC",
            exp.DataType.Type.DATETIME: "DATETIME2",
            exp.DataType.Type.DOUBLE: "FLOAT",
            exp.DataType.Type.INT: "INTEGER",
            exp.DataType.Type.TIMESTAMP: "DATETIME2",
            exp.DataType.Type.TIMESTAMPTZ: "DATETIMEOFFSET",
            exp.DataType.Type.VARIANT: "SQL_VARIANT",
        }

        TRANSFORMS = {
            **generator.Generator.TRANSFORMS,
            exp.AnyValue: any_value_to_max_sql,
            exp.AutoIncrementColumnConstraint: lambda *_: "IDENTITY",
            exp.DateAdd: generate_date_delta_with_unit_sql,
            exp.DateDiff: generate_date_delta_with_unit_sql,
            exp.CurrentDate: rename_func("GETDATE"),
            exp.CurrentTimestamp: rename_func("GETDATE"),
            exp.Extract: rename_func("DATEPART"),
            exp.GroupConcat: _string_agg_sql,
            exp.If: rename_func("IIF"),
            exp.Insert: move_insert_cte_sql,
            exp.Max: max_or_greatest,
            exp.MD5: lambda self, e: self.func("HASHBYTES", exp.Literal.string("MD5"), e.this),
            exp.Min: min_or_least,
            exp.NumberToStr: _format_sql,
            exp.Select: transforms.preprocess(
                [
                    transforms.eliminate_distinct_on,
                    transforms.eliminate_semi_and_anti_joins,
                    transforms.eliminate_qualify,
                ]
            ),
            exp.SHA: lambda self, e: self.func("HASHBYTES", exp.Literal.string("SHA1"), e.this),
            exp.SHA2: lambda self, e: self.func(
                "HASHBYTES",
                exp.Literal.string(f"SHA2_{e.args.get('length', 256)}"),
                e.this,
            ),
            exp.TemporaryProperty: lambda self, e: "",
            exp.TimeStrToTime: timestrtotime_sql,
            exp.TimeToStr: _format_sql,
            exp.TsOrDsToDate: ts_or_ds_to_date_sql("tsql"),
        }

        TRANSFORMS.pop(exp.ReturnsProperty)

        PROPERTIES_LOCATION = {
            **generator.Generator.PROPERTIES_LOCATION,
            exp.VolatileProperty: exp.Properties.Location.UNSUPPORTED,
        }

        def setitem_sql(self, expression: exp.SetItem) -> str:
            this = expression.this
            if isinstance(this, exp.EQ) and not isinstance(this.left, exp.Parameter):
                # T-SQL does not use '=' in SET command, except when the LHS is a variable.
                return f"{self.sql(this.left)} {self.sql(this.right)}"

            return super().setitem_sql(expression)

        def boolean_sql(self, expression: exp.Boolean) -> str:
            if type(expression.parent) in BIT_TYPES:
                return "1" if expression.this else "0"

            return "(1 = 1)" if expression.this else "(1 = 0)"

        def is_sql(self, expression: exp.Is) -> str:
            if isinstance(expression.expression, exp.Boolean):
                return self.binary(expression, "=")
            return self.binary(expression, "IS")

        def createable_sql(self, expression: exp.Create, locations: t.DefaultDict) -> str:
            sql = self.sql(expression, "this")
            properties = expression.args.get("properties")

            if sql[:1] != "#" and any(
                isinstance(prop, exp.TemporaryProperty)
                for prop in (properties.expressions if properties else [])
            ):
                sql = f"#{sql}"

            return sql

        def create_sql(self, expression: exp.Create) -> str:
            expression = expression.copy()
            kind = self.sql(expression, "kind").upper()
            exists = expression.args.pop("exists", None)
            sql = super().create_sql(expression)

            table = expression.find(exp.Table)

            if kind == "TABLE" and expression.expression:
                sql = f"SELECT * INTO {self.sql(table)} FROM ({self.sql(expression.expression)}) AS temp"

            if exists:
                identifier = self.sql(exp.Literal.string(exp.table_name(table) if table else ""))
                sql = self.sql(exp.Literal.string(sql))
                if kind == "SCHEMA":
                    sql = f"""IF NOT EXISTS (SELECT * FROM information_schema.schemata WHERE schema_name = {identifier}) EXEC({sql})"""
                elif kind == "TABLE":
                    assert table
                    where = exp.and_(
                        exp.column("table_name").eq(table.name),
                        exp.column("table_schema").eq(table.db) if table.db else None,
                        exp.column("table_catalog").eq(table.catalog) if table.catalog else None,
                    )
                    sql = f"""IF NOT EXISTS (SELECT * FROM information_schema.tables WHERE {where}) EXEC({sql})"""
                elif kind == "INDEX":
                    index = self.sql(exp.Literal.string(expression.this.text("this")))
                    sql = f"""IF NOT EXISTS (SELECT * FROM sys.indexes WHERE object_id = object_id({identifier}) AND name = {index}) EXEC({sql})"""
            elif expression.args.get("replace"):
                sql = sql.replace("CREATE OR REPLACE ", "CREATE OR ALTER ", 1)

            return sql

        def offset_sql(self, expression: exp.Offset) -> str:
            return f"{super().offset_sql(expression)} ROWS"

        def version_sql(self, expression: exp.Version) -> str:
            name = "SYSTEM_TIME" if expression.name == "TIMESTAMP" else expression.name
            this = f"FOR {name}"
            expr = expression.expression
            kind = expression.text("kind")
            if kind in ("FROM", "BETWEEN"):
                args = expr.expressions
                sep = "TO" if kind == "FROM" else "AND"
                expr_sql = f"{self.sql(seq_get(args, 0))} {sep} {self.sql(seq_get(args, 1))}"
            else:
                expr_sql = self.sql(expr)

            expr_sql = f" {expr_sql}" if expr_sql else ""
            return f"{this} {kind}{expr_sql}"

        def returnsproperty_sql(self, expression: exp.ReturnsProperty) -> str:
            table = expression.args.get("table")
            table = f"{table} " if table else ""
            return f"RETURNS {table}{self.sql(expression, 'this')}"

        def returning_sql(self, expression: exp.Returning) -> str:
            into = self.sql(expression, "into")
            into = self.seg(f"INTO {into}") if into else ""
            return f"{self.seg('OUTPUT')} {self.expressions(expression, flat=True)}{into}"

        def transaction_sql(self, expression: exp.Transaction) -> str:
            this = self.sql(expression, "this")
            this = f" {this}" if this else ""
            mark = self.sql(expression, "mark")
            mark = f" WITH MARK {mark}" if mark else ""
            return f"BEGIN TRANSACTION{this}{mark}"

        def commit_sql(self, expression: exp.Commit) -> str:
            this = self.sql(expression, "this")
            this = f" {this}" if this else ""
            durability = expression.args.get("durability")
            durability = (
                f" WITH (DELAYED_DURABILITY = {'ON' if durability else 'OFF'})"
                if durability is not None
                else ""
            )
            return f"COMMIT TRANSACTION{this}{durability}"

        def rollback_sql(self, expression: exp.Rollback) -> str:
            this = self.sql(expression, "this")
            this = f" {this}" if this else ""
            return f"ROLLBACK TRANSACTION{this}"

        def identifier_sql(self, expression: exp.Identifier) -> str:
            identifier = super().identifier_sql(expression)

            if expression.args.get("global"):
                identifier = f"##{identifier}"
            elif expression.args.get("temporary"):
                identifier = f"#{identifier}"

            return identifier

        def constraint_sql(self, expression: exp.Constraint) -> str:
            this = self.sql(expression, "this")
            expressions = self.expressions(expression, flat=True, sep=" ")
            return f"CONSTRAINT {this} {expressions}"

        # https://learn.microsoft.com/en-us/answers/questions/448821/create-table-in-sql-server
        def generatedasidentitycolumnconstraint_sql(
            self, expression: exp.GeneratedAsIdentityColumnConstraint
        ) -> str:
            start = self.sql(expression, "start") or "1"
            increment = self.sql(expression, "increment") or "1"
            return f"IDENTITY({start}, {increment})"