sqlglot API documentation

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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, Spark, 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 the SQLGlot API in the documentation.

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

## Table of Contents

- Install
- Versioning
- Get in Touch
- Examples
  - Formatting and Transpiling
  - Metadata
  - Parser Errors
  - Unsupported Errors
  - Build and Modify SQL
  - SQL Optimizer
  - AST Introspection
  - AST Diff
  - Custom Dialects
  - SQL Execution
- Used By
- Documentation
- Run Tests and Lint
- Benchmarks
- Optional Dependencies

## Install

From PyPI:

    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!

## 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)

### 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)))),
      Move(expression=(COLUMN this:
        (IDENTIFIER this: c, quoted: False))),
      Keep(source=(IDENTIFIER this: b, quoted: False), target=(IDENTIFIER this: b, 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

- SQLMesh
- Fugue
- ibis
- mysql-mimic
- Querybook
- Quokka
- Splink

## 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 3.10.5 in seconds.

Query | sqlglot | sqlfluff | sqltree | sqlparse | moz_sql_parser | sqloxide
--- | --- | --- | --- | --- | --- | ---
tpch | 0.01308 (1.0) | 1.60626 (122.7) | 0.01168 (0.893) | 0.04958 (3.791) | 0.08543 (6.531) | 0.00136 (0.104)
short | 0.00109 (1.0) | 0.14134 (129.2) | 0.00099 (0.906) | 0.00342 (3.131) | 0.00652 (5.970) | 8.76E-5 (0.080)
long | 0.01399 (1.0) | 2.12632 (151.9) | 0.01126 (0.805) | 0.04410 (3.151) | 0.06671 (4.767) | 0.00107 (0.076)
crazy | 0.03969 (1.0) | 24.3777 (614.1) | 0.03917 (0.987) | 11.7043 (294.8) | 1.03280 (26.02) | 0.00625 (0.157)

## 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

View Source

      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    cast as cast,
     26    column as column,
     27    condition as condition,
     28    except_ as except_,
     29    from_ as from_,
     30    func as func,
     31    intersect as intersect,
     32    maybe_parse as maybe_parse,
     33    not_ as not_,
     34    or_ as or_,
     35    select as select,
     36    subquery as subquery,
     37    table_ as table,
     38    to_column as to_column,
     39    to_identifier as to_identifier,
     40    to_table as to_table,
     41    union as union,
     42)
     43from sqlglot.generator import Generator as Generator
     44from sqlglot.parser import Parser as Parser
     45from sqlglot.schema import MappingSchema as MappingSchema, Schema as Schema
     46from sqlglot.tokens import Tokenizer as Tokenizer, TokenType as TokenType
     47
     48if t.TYPE_CHECKING:
     49    from sqlglot._typing import E
     50    from sqlglot.dialects.dialect import DialectType as DialectType
     51
     52logger = logging.getLogger("sqlglot")
     53
     54
     55try:
     56    from sqlglot._version import __version__, __version_tuple__
     57except ImportError:
     58    logger.error(
     59        "Unable to set __version__, run `pip install -e .` or `python setup.py develop` first."
     60    )
     61
     62
     63pretty = False
     64"""Whether to format generated SQL by default."""
     65
     66schema = MappingSchema()
     67"""The default schema used by SQLGlot (e.g. in the optimizer)."""
     68
     69
     70def parse(
     71    sql: str, read: DialectType = None, dialect: DialectType = None, **opts
     72) -> t.List[t.Optional[Expression]]:
     73    """
     74    Parses the given SQL string into a collection of syntax trees, one per parsed SQL statement.
     75
     76    Args:
     77        sql: the SQL code string to parse.
     78        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
     79        dialect: the SQL dialect (alias for read).
     80        **opts: other `sqlglot.parser.Parser` options.
     81
     82    Returns:
     83        The resulting syntax tree collection.
     84    """
     85    dialect = Dialect.get_or_raise(read or dialect)()
     86    return dialect.parse(sql, **opts)
     87
     88
     89@t.overload
     90def parse_one(sql: str, *, into: t.Type[E], **opts) -> E:
     91    ...
     92
     93
     94@t.overload
     95def parse_one(sql: str, **opts) -> Expression:
     96    ...
     97
     98
     99def parse_one(
    100    sql: str,
    101    read: DialectType = None,
    102    dialect: DialectType = None,
    103    into: t.Optional[exp.IntoType] = None,
    104    **opts,
    105) -> Expression:
    106    """
    107    Parses the given SQL string and returns a syntax tree for the first parsed SQL statement.
    108
    109    Args:
    110        sql: the SQL code string to parse.
    111        read: the SQL dialect to apply during parsing (eg. "spark", "hive", "presto", "mysql").
    112        dialect: the SQL dialect (alias for read)
    113        into: the SQLGlot Expression to parse into.
    114        **opts: other `sqlglot.parser.Parser` options.
    115
    116    Returns:
    117        The syntax tree for the first parsed statement.
    118    """
    119
    120    dialect = Dialect.get_or_raise(read or dialect)()
    121
    122    if into:
    123        result = dialect.parse_into(into, sql, **opts)
    124    else:
    125        result = dialect.parse(sql, **opts)
    126
    127    for expression in result:
    128        if not expression:
    129            raise ParseError(f"No expression was parsed from '{sql}'")
    130        return expression
    131    else:
    132        raise ParseError(f"No expression was parsed from '{sql}'")
    133
    134
    135def transpile(
    136    sql: str,
    137    read: DialectType = None,
    138    write: DialectType = None,
    139    identity: bool = True,
    140    error_level: t.Optional[ErrorLevel] = None,
    141    **opts,
    142) -> t.List[str]:
    143    """
    144    Parses the given SQL string in accordance with the source dialect and returns a list of SQL strings transformed
    145    to conform to the target dialect. Each string in the returned list represents a single transformed SQL statement.
    146
    147    Args:
    148        sql: the SQL code string to transpile.
    149        read: the source dialect used to parse the input string (eg. "spark", "hive", "presto", "mysql").
    150        write: the target dialect into which the input should be transformed (eg. "spark", "hive", "presto", "mysql").
    151        identity: if set to `True` and if the target dialect is not specified the source dialect will be used as both:
    152            the source and the target dialect.
    153        error_level: the desired error level of the parser.
    154        **opts: other `sqlglot.generator.Generator` options.
    155
    156    Returns:
    157        The list of transpiled SQL statements.
    158    """
    159    write = (read if write is None else write) if identity else write
    160    return [
    161        Dialect.get_or_raise(write)().generate(expression, **opts)
    162        for expression in parse(sql, read, error_level=error_level)
    163    ]

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]]: View Source

    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    dialect = Dialect.get_or_raise(read or dialect)()
    87    return 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: View Source

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

    136def transpile(
    137    sql: str,
    138    read: DialectType = None,
    139    write: DialectType = None,
    140    identity: bool = True,
    141    error_level: t.Optional[ErrorLevel] = None,
    142    **opts,
    143) -> t.List[str]:
    144    """
    145    Parses the given SQL string in accordance with the source dialect and returns a list of SQL strings transformed
    146    to conform to the target dialect. Each string in the returned list represents a single transformed SQL statement.
    147
    148    Args:
    149        sql: the SQL code string to transpile.
    150        read: the source dialect used to parse the input string (eg. "spark", "hive", "presto", "mysql").
    151        write: the target dialect into which the input should be transformed (eg. "spark", "hive", "presto", "mysql").
    152        identity: if set to `True` and if the target dialect is not specified the source dialect will be used as both:
    153            the source and the target dialect.
    154        error_level: the desired error level of the parser.
    155        **opts: other `sqlglot.generator.Generator` options.
    156
    157    Returns:
    158        The list of transpiled SQL statements.
    159    """
    160    write = (read if write is None else write) if identity else write
    161    return [
    162        Dialect.get_or_raise(write)().generate(expression, **opts)
    163        for expression in parse(sql, read, error_level=error_level)
    164    ]

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.