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SQLGlot is a no-dependency SQL parser, transpiler, optimizer, and engine. It can be used to format SQL or translate between 20 different dialects like DuckDB, Presto / Trino, Spark / Databricks, Snowflake, and BigQuery. It aims to read a wide variety of SQL inputs and output syntactically and semantically correct SQL in the targeted dialects.

It is a very comprehensive generic SQL parser with a robust test suite. It is also quite performant, while being written purely in Python.

You can easily customize the parser, analyze queries, traverse expression trees, and programmatically build SQL.

Syntax errors are highlighted and dialect incompatibilities can warn or raise depending on configurations. However, it should be noted that SQL validation is not SQLGlot’s goal, so some syntax errors may go unnoticed.

Learn more about SQLGlot in the API documentation and the expression tree primer.

Contributions are very welcome in SQLGlot; read the contribution guide to get started!

Table of Contents

Install

From PyPI:

pip3 install "sqlglot[rs]"

# Without Rust tokenizer (slower):
# pip3 install sqlglot

Or with a local checkout:

make install

Requirements for development (optional):

make install-dev

Versioning

Given a version number MAJOR.MINOR.PATCH, SQLGlot uses the following versioning strategy:

  • The PATCH version is incremented when there are backwards-compatible fixes or feature additions.
  • The MINOR version is incremented when there are backwards-incompatible fixes or feature additions.
  • The MAJOR version is incremented when there are significant backwards-incompatible fixes or feature additions.

Get in Touch

We'd love to hear from you. Join our community Slack channel!

FAQ

I tried to parse SQL that should be valid but it failed, why did that happen?

  • You need to specify the dialect to read the SQL properly, by default it is SQLGlot's dialect which is designed to be a superset of all dialects parse_one(sql, dialect="spark"). If you tried specifying the dialect and it still doesn't work, please file an issue.

I tried to output SQL but it's not in the correct dialect!

  • You need to specify the dialect to write the sql properly, by default it is in SQLGlot's dialect parse_one(sql, dialect="spark").sql(dialect="spark").

I tried to parse invalid SQL and it should raise an error but it worked! Why didn't it validate my SQL.

  • SQLGlot is not a validator and designed to be very forgiving, handling things like trailing commas.

Examples

Formatting and Transpiling

Easily translate from one dialect to another. For example, date/time functions vary between dialects and can be hard to deal with:

import sqlglot
transpile("SELECT EPOCH_MS(1618088028295)", read="duckdb", write="hive")[0]
'SELECT FROM_UNIXTIME(1618088028295 / 1000)'

SQLGlot can even translate custom time formats:

import sqlglot
transpile("SELECT STRFTIME(x, '%y-%-m-%S')", read="duckdb", write="hive")[0]
"SELECT DATE_FORMAT(x, 'yy-M-ss')"

As another example, let's suppose that we want to read in a SQL query that contains a CTE and a cast to REAL, and then transpile it to Spark, which uses backticks for identifiers and FLOAT instead of REAL:

import sqlglot

sql = """WITH baz AS (SELECT a, c FROM foo WHERE a = 1) SELECT f.a, b.b, baz.c, CAST("b"."a" AS REAL) d FROM foo f JOIN bar b ON f.a = b.a LEFT JOIN baz ON f.a = baz.a"""
print(transpile(sql, write="spark", identify=True, pretty=True)[0])
WITH `baz` AS (
  SELECT
    `a`,
    `c`
  FROM `foo`
  WHERE
    `a` = 1
)
SELECT
  `f`.`a`,
  `b`.`b`,
  `baz`.`c`,
  CAST(`b`.`a` AS FLOAT) AS `d`
FROM `foo` AS `f`
JOIN `bar` AS `b`
  ON `f`.`a` = `b`.`a`
LEFT JOIN `baz`
  ON `f`.`a` = `baz`.`a`

Comments are also preserved on a best-effort basis when transpiling SQL code:

sql = """
/* multi
   line
   comment
*/
SELECT
  tbl.cola /* comment 1 */ + tbl.colb /* comment 2 */,
  CAST(x AS INT), # comment 3
  y               -- comment 4
FROM
  bar /* comment 5 */,
  tbl #          comment 6
"""

print(transpile(sql, read='mysql', pretty=True)[0])
/* multi
   line
   comment
*/
SELECT
  tbl.cola /* comment 1 */ + tbl.colb /* comment 2 */,
  CAST(x AS INT), /* comment 3 */
  y /* comment 4 */
FROM bar /* comment 5 */, tbl /*          comment 6 */

Metadata

You can explore SQL with expression helpers to do things like find columns and tables:

from sqlglot import parse_one, exp

# print all column references (a and b)
for column in parse_one("SELECT a, b + 1 AS c FROM d").find_all(exp.Column):
    print(column.alias_or_name)

# find all projections in select statements (a and c)
for select in parse_one("SELECT a, b + 1 AS c FROM d").find_all(exp.Select):
    for projection in select.expressions:
        print(projection.alias_or_name)

# find all tables (x, y, z)
for table in parse_one("SELECT * FROM x JOIN y JOIN z").find_all(exp.Table):
    print(table.name)

Read the ast primer to learn more about SQLGlot's internals.

Parser Errors

When the parser detects an error in the syntax, it raises a ParseError:

import sqlglot
transpile("SELECT foo( FROM bar")
sqlglot.errors.ParseError: Expecting ). Line 1, Col: 13.
  select foo( FROM bar
              ~~~~

Structured syntax errors are accessible for programmatic use:

import sqlglot
try:
    transpile("SELECT foo( FROM bar")
except sqlglot.errors.ParseError as e:
    print(e.errors)
[{
  'description': 'Expecting )',
  'line': 1,
  'col': 16,
  'start_context': 'SELECT foo( ',
  'highlight': 'FROM',
  'end_context': ' bar',
  'into_expression': None,
}]

Unsupported Errors

Presto APPROX_DISTINCT supports the accuracy argument which is not supported in Hive:

import sqlglot
transpile("SELECT APPROX_DISTINCT(a, 0.1) FROM foo", read="presto", write="hive")
APPROX_COUNT_DISTINCT does not support accuracy
'SELECT APPROX_COUNT_DISTINCT(a) FROM foo'

Build and Modify SQL

SQLGlot supports incrementally building sql expressions:

from sqlglot import select, condition

where = condition("x=1").and_("y=1")
select("*").from_("y").where(where).sql()
'SELECT * FROM y WHERE x = 1 AND y = 1'

You can also modify a parsed tree:

from sqlglot import parse_one
parse_one("SELECT x FROM y").from_("z").sql()
'SELECT x FROM z'

There is also a way to recursively transform the parsed tree by applying a mapping function to each tree node:

from sqlglot import exp, parse_one

expression_tree = parse_one("SELECT a FROM x")

def transformer(node):
    if isinstance(node, exp.Column) and node.name == "a":
        return parse_one("FUN(a)")
    return node

transformed_tree = expression_tree.transform(transformer)
transformed_tree.sql()
'SELECT FUN(a) FROM x'

SQL Optimizer

SQLGlot can rewrite queries into an "optimized" form. It performs a variety of techniques to create a new canonical AST. This AST can be used to standardize queries or provide the foundations for implementing an actual engine. For example:

import sqlglot
from sqlglot.optimizer import optimize

print(
    optimize(
        parse_one("""
            SELECT A OR (B OR (C AND D))
            FROM x
            WHERE Z = date '2021-01-01' + INTERVAL '1' month OR 1 = 0
        """),
        schema={"x": {"A": "INT", "B": "INT", "C": "INT", "D": "INT", "Z": "STRING"}}
    ).sql(pretty=True)
)
SELECT
  (
    "x"."a" <> 0 OR "x"."b" <> 0 OR "x"."c" <> 0
  )
  AND (
    "x"."a" <> 0 OR "x"."b" <> 0 OR "x"."d" <> 0
  ) AS "_col_0"
FROM "x" AS "x"
WHERE
  CAST("x"."z" AS DATE) = CAST('2021-02-01' AS DATE)

AST Introspection

You can see the AST version of the sql by calling repr:

from sqlglot import parse_one
print(repr(parse_one("SELECT a + 1 AS z")))
Select(
  expressions=[
    Alias(
      this=Add(
        this=Column(
          this=Identifier(this=a, quoted=False)),
        expression=Literal(this=1, is_string=False)),
      alias=Identifier(this=z, quoted=False))])

AST Diff

SQLGlot can calculate the difference between two expressions and output changes in a form of a sequence of actions needed to transform a source expression into a target one:

from sqlglot import diff, parse_one
diff(parse_one("SELECT a + b, c, d"), parse_one("SELECT c, a - b, d"))
[
  Remove(expression=Add(
    this=Column(
      this=Identifier(this=a, quoted=False)),
    expression=Column(
      this=Identifier(this=b, quoted=False)))),
  Insert(expression=Sub(
    this=Column(
      this=Identifier(this=a, quoted=False)),
    expression=Column(
      this=Identifier(this=b, quoted=False)))),
  Keep(source=Identifier(this=d, quoted=False), target=Identifier(this=d, quoted=False)),
  ...
]

See also: Semantic Diff for SQL.

Custom Dialects

Dialects can be added by subclassing Dialect:

from sqlglot import exp
from sqlglot.dialects.dialect import Dialect
from sqlglot.generator import Generator
from sqlglot.tokens import Tokenizer, TokenType


class Custom(Dialect):
    class Tokenizer(Tokenizer):
        QUOTES = ["'", '"']
        IDENTIFIERS = ["`"]

        KEYWORDS = {
            **Tokenizer.KEYWORDS,
            "INT64": TokenType.BIGINT,
            "FLOAT64": TokenType.DOUBLE,
        }

    class Generator(Generator):
        TRANSFORMS = {exp.Array: lambda self, e: f"[{self.expressions(e)}]"}

        TYPE_MAPPING = {
            exp.DataType.Type.TINYINT: "INT64",
            exp.DataType.Type.SMALLINT: "INT64",
            exp.DataType.Type.INT: "INT64",
            exp.DataType.Type.BIGINT: "INT64",
            exp.DataType.Type.DECIMAL: "NUMERIC",
            exp.DataType.Type.FLOAT: "FLOAT64",
            exp.DataType.Type.DOUBLE: "FLOAT64",
            exp.DataType.Type.BOOLEAN: "BOOL",
            exp.DataType.Type.TEXT: "STRING",
        }

print(Dialect["custom"])
<class '__main__.Custom'>

SQL Execution

One can even interpret SQL queries using SQLGlot, where the tables are represented as Python dictionaries. Although the engine is not very fast (it's not supposed to be) and is in a relatively early stage of development, it can be useful for unit testing and running SQL natively across Python objects. Additionally, the foundation can be easily integrated with fast compute kernels (arrow, pandas). Below is an example showcasing the execution of a SELECT expression that involves aggregations and JOINs:

from sqlglot.executor import execute

tables = {
    "sushi": [
        {"id": 1, "price": 1.0},
        {"id": 2, "price": 2.0},
        {"id": 3, "price": 3.0},
    ],
    "order_items": [
        {"sushi_id": 1, "order_id": 1},
        {"sushi_id": 1, "order_id": 1},
        {"sushi_id": 2, "order_id": 1},
        {"sushi_id": 3, "order_id": 2},
    ],
    "orders": [
        {"id": 1, "user_id": 1},
        {"id": 2, "user_id": 2},
    ],
}

execute(
    """
    SELECT
      o.user_id,
      SUM(s.price) AS price
    FROM orders o
    JOIN order_items i
      ON o.id = i.order_id
    JOIN sushi s
      ON i.sushi_id = s.id
    GROUP BY o.user_id
    """,
    tables=tables
)
user_id price
      1   4.0
      2   3.0

See also: Writing a Python SQL engine from scratch.

Used By

Documentation

SQLGlot uses pdoc to serve its API documentation.

A hosted version is on the SQLGlot website, or you can build locally with:

make docs-serve

Run Tests and Lint

make style  # Only linter checks
make unit   # Only unit tests
make check  # Full test suite & linter checks

Benchmarks

Benchmarks run on Python 3.10.12 in seconds.

Query sqlglot sqlglotrs sqlfluff sqltree sqlparse moz_sql_parser sqloxide
tpch 0.00944 (1.0) 0.00590 (0.625) 0.32116 (33.98) 0.00693 (0.734) 0.02858 (3.025) 0.03337 (3.532) 0.00073 (0.077)
short 0.00065 (1.0) 0.00044 (0.687) 0.03511 (53.82) 0.00049 (0.759) 0.00163 (2.506) 0.00234 (3.601) 0.00005 (0.073)
long 0.00889 (1.0) 0.00572 (0.643) 0.36982 (41.56) 0.00614 (0.690) 0.02530 (2.844) 0.02931 (3.294) 0.00059 (0.066)
crazy 0.02918 (1.0) 0.01991 (0.682) 1.88695 (64.66) 0.02003 (0.686) 7.46894 (255.9) 0.64994 (22.27) 0.00327 (0.112)

Optional Dependencies

SQLGlot uses dateutil to simplify literal timedelta expressions. The optimizer will not simplify expressions like the following if the module cannot be found:

x + interval '1' month

  1"""
  2.. include:: ../README.md
  3
  4----
  5"""
  6
  7from __future__ import annotations
  8
  9import logging
 10import typing as t
 11
 12from sqlglot import expressions as exp
 13from sqlglot.dialects.dialect import Dialect as Dialect, Dialects as Dialects
 14from sqlglot.diff import diff as diff
 15from sqlglot.errors import (
 16    ErrorLevel as ErrorLevel,
 17    ParseError as ParseError,
 18    TokenError as TokenError,
 19    UnsupportedError as UnsupportedError,
 20)
 21from sqlglot.expressions import (
 22    Expression as Expression,
 23    alias_ as alias,
 24    and_ as and_,
 25    case as case,
 26    cast as cast,
 27    column as column,
 28    condition as condition,
 29    except_ as except_,
 30    from_ as from_,
 31    func as func,
 32    intersect as intersect,
 33    maybe_parse as maybe_parse,
 34    not_ as not_,
 35    or_ as or_,
 36    select as select,
 37    subquery as subquery,
 38    table_ as table,
 39    to_column as to_column,
 40    to_identifier as to_identifier,
 41    to_table as to_table,
 42    union as union,
 43)
 44from sqlglot.generator import Generator as Generator
 45from sqlglot.parser import Parser as Parser
 46from sqlglot.schema import MappingSchema as MappingSchema, Schema as Schema
 47from sqlglot.tokens import Tokenizer as Tokenizer, TokenType as TokenType
 48
 49if t.TYPE_CHECKING:
 50    from sqlglot._typing import E
 51    from sqlglot.dialects.dialect import DialectType as DialectType
 52
 53logger = logging.getLogger("sqlglot")
 54
 55
 56try:
 57    from sqlglot._version import __version__, __version_tuple__
 58except ImportError:
 59    logger.error(
 60        "Unable to set __version__, run `pip install -e .` or `python setup.py develop` first."
 61    )
 62
 63
 64pretty = False
 65"""Whether to format generated SQL by default."""
 66
 67schema = MappingSchema()
 68"""The default schema used by SQLGlot (e.g. in the optimizer)."""
 69
 70
 71def parse(
 72    sql: str, read: DialectType = None, dialect: DialectType = None, **opts
 73) -> t.List[t.Optional[Expression]]:
 74    """
 75    Parses the given SQL string into a collection of syntax trees, one per parsed SQL statement.
 76
 77    Args:
 78        sql: the SQL code string to parse.
 79        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
 80        dialect: the SQL dialect (alias for read).
 81        **opts: other `sqlglot.parser.Parser` options.
 82
 83    Returns:
 84        The resulting syntax tree collection.
 85    """
 86    return Dialect.get_or_raise(read or dialect).parse(sql, **opts)
 87
 88
 89@t.overload
 90def parse_one(sql: str, *, into: t.Type[E], **opts) -> E: ...
 91
 92
 93@t.overload
 94def parse_one(sql: str, **opts) -> Expression: ...
 95
 96
 97def parse_one(
 98    sql: str,
 99    read: DialectType = None,
100    dialect: DialectType = None,
101    into: t.Optional[exp.IntoType] = None,
102    **opts,
103) -> Expression:
104    """
105    Parses the given SQL string and returns a syntax tree for the first parsed SQL statement.
106
107    Args:
108        sql: the SQL code string to parse.
109        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
110        dialect: the SQL dialect (alias for read)
111        into: the SQLGlot Expression to parse into.
112        **opts: other `sqlglot.parser.Parser` options.
113
114    Returns:
115        The syntax tree for the first parsed statement.
116    """
117
118    dialect = Dialect.get_or_raise(read or dialect)
119
120    if into:
121        result = dialect.parse_into(into, sql, **opts)
122    else:
123        result = dialect.parse(sql, **opts)
124
125    for expression in result:
126        if not expression:
127            raise ParseError(f"No expression was parsed from '{sql}'")
128        return expression
129    else:
130        raise ParseError(f"No expression was parsed from '{sql}'")
131
132
133def transpile(
134    sql: str,
135    read: DialectType = None,
136    write: DialectType = None,
137    identity: bool = True,
138    error_level: t.Optional[ErrorLevel] = None,
139    **opts,
140) -> t.List[str]:
141    """
142    Parses the given SQL string in accordance with the source dialect and returns a list of SQL strings transformed
143    to conform to the target dialect. Each string in the returned list represents a single transformed SQL statement.
144
145    Args:
146        sql: the SQL code string to transpile.
147        read: the source dialect used to parse the input string (eg. "spark", "hive", "presto", "mysql").
148        write: the target dialect into which the input should be transformed (eg. "spark", "hive", "presto", "mysql").
149        identity: if set to `True` and if the target dialect is not specified the source dialect will be used as both:
150            the source and the target dialect.
151        error_level: the desired error level of the parser.
152        **opts: other `sqlglot.generator.Generator` options.
153
154    Returns:
155        The list of transpiled SQL statements.
156    """
157    write = (read if write is None else write) if identity else write
158    write = Dialect.get_or_raise(write)
159    return [
160        write.generate(expression, copy=False, **opts) if expression else ""
161        for expression in parse(sql, read, error_level=error_level)
162    ]
logger = <Logger sqlglot (WARNING)>
pretty = False

Whether to format generated SQL by default.

schema = <sqlglot.schema.MappingSchema object>

The default schema used by SQLGlot (e.g. in the optimizer).

def parse( sql: str, read: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, dialect: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, **opts) -> List[Optional[sqlglot.expressions.Expression]]:
72def parse(
73    sql: str, read: DialectType = None, dialect: DialectType = None, **opts
74) -> t.List[t.Optional[Expression]]:
75    """
76    Parses the given SQL string into a collection of syntax trees, one per parsed SQL statement.
77
78    Args:
79        sql: the SQL code string to parse.
80        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
81        dialect: the SQL dialect (alias for read).
82        **opts: other `sqlglot.parser.Parser` options.
83
84    Returns:
85        The resulting syntax tree collection.
86    """
87    return Dialect.get_or_raise(read or dialect).parse(sql, **opts)

Parses the given SQL string into a collection of syntax trees, one per parsed SQL statement.

Arguments:
  • sql: the SQL code string to parse.
  • read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
  • dialect: the SQL dialect (alias for read).
  • **opts: other sqlglot.parser.Parser options.
Returns:

The resulting syntax tree collection.

def parse_one( sql: str, read: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, dialect: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, into: Union[str, Type[sqlglot.expressions.Expression], Collection[Union[str, Type[sqlglot.expressions.Expression]]], NoneType] = None, **opts) -> sqlglot.expressions.Expression:
 98def parse_one(
 99    sql: str,
100    read: DialectType = None,
101    dialect: DialectType = None,
102    into: t.Optional[exp.IntoType] = None,
103    **opts,
104) -> Expression:
105    """
106    Parses the given SQL string and returns a syntax tree for the first parsed SQL statement.
107
108    Args:
109        sql: the SQL code string to parse.
110        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
111        dialect: the SQL dialect (alias for read)
112        into: the SQLGlot Expression to parse into.
113        **opts: other `sqlglot.parser.Parser` options.
114
115    Returns:
116        The syntax tree for the first parsed statement.
117    """
118
119    dialect = Dialect.get_or_raise(read or dialect)
120
121    if into:
122        result = dialect.parse_into(into, sql, **opts)
123    else:
124        result = dialect.parse(sql, **opts)
125
126    for expression in result:
127        if not expression:
128            raise ParseError(f"No expression was parsed from '{sql}'")
129        return expression
130    else:
131        raise ParseError(f"No expression was parsed from '{sql}'")

Parses the given SQL string and returns a syntax tree for the first parsed SQL statement.

Arguments:
  • sql: the SQL code string to parse.
  • read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
  • dialect: the SQL dialect (alias for read)
  • into: the SQLGlot Expression to parse into.
  • **opts: other sqlglot.parser.Parser options.
Returns:

The syntax tree for the first parsed statement.

def transpile( sql: str, read: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, write: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, identity: bool = True, error_level: Optional[sqlglot.errors.ErrorLevel] = None, **opts) -> List[str]:
134def transpile(
135    sql: str,
136    read: DialectType = None,
137    write: DialectType = None,
138    identity: bool = True,
139    error_level: t.Optional[ErrorLevel] = None,
140    **opts,
141) -> t.List[str]:
142    """
143    Parses the given SQL string in accordance with the source dialect and returns a list of SQL strings transformed
144    to conform to the target dialect. Each string in the returned list represents a single transformed SQL statement.
145
146    Args:
147        sql: the SQL code string to transpile.
148        read: the source dialect used to parse the input string (eg. "spark", "hive", "presto", "mysql").
149        write: the target dialect into which the input should be transformed (eg. "spark", "hive", "presto", "mysql").
150        identity: if set to `True` and if the target dialect is not specified the source dialect will be used as both:
151            the source and the target dialect.
152        error_level: the desired error level of the parser.
153        **opts: other `sqlglot.generator.Generator` options.
154
155    Returns:
156        The list of transpiled SQL statements.
157    """
158    write = (read if write is None else write) if identity else write
159    write = Dialect.get_or_raise(write)
160    return [
161        write.generate(expression, copy=False, **opts) if expression else ""
162        for expression in parse(sql, read, error_level=error_level)
163    ]

Parses the given SQL string in accordance with the source dialect and returns a list of SQL strings transformed to conform to the target dialect. Each string in the returned list represents a single transformed SQL statement.

Arguments:
  • sql: the SQL code string to transpile.
  • read: the source dialect used to parse the input string (eg. "spark", "hive", "presto", "mysql").
  • write: the target dialect into which the input should be transformed (eg. "spark", "hive", "presto", "mysql").
  • identity: if set to True and if the target dialect is not specified the source dialect will be used as both: the source and the target dialect.
  • error_level: the desired error level of the parser.
  • **opts: other sqlglot.generator.Generator options.
Returns:

The list of transpiled SQL statements.