SQLGlot is a no-dependency SQL parser, transpiler, optimizer, and engine. It can be used to format SQL or translate between 19 different dialects like DuckDB, Presto, Spark, Snowflake, and BigQuery. It aims to read a wide variety of SQL inputs and output syntactically 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 from dialects and can be hard to deal with:

importsqlglotsqlglot.transpile("SELECT EPOCH_MS(1618088028295)", read="duckdb", write="hive")[0]

'SELECT FROM_UNIXTIME(1618088028295 / 1000)'

SQLGlot can even translate custom time formats:

importsqlglotsqlglot.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:

importsqlglotsql="""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(sqlglot.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 in 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 4FROM bar /* comment 5 */, tbl # comment 6"""print(sqlglot.transpile(sql, read='mysql', pretty=True)[0])

/* multi line comment*/SELECTtbl.cola/* comment 1 */+tbl.colb/* comment 2 */,
CAST(x ASINT), /* 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:

fromsqlglotimportparse_one, exp# print all column references (a and b)forcolumninparse_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)forselectinparse_one("SELECT a, b + 1 AS c FROM d").find_all(exp.Select):
forprojectioninselect.expressions:
print(projection.alias_or_name)
# find all tables (x, y, z)fortableinparse_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 ParserError:

importsqlglotsqlglot.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:

importsqlglottry:
sqlglot.transpile("SELECT foo( FROM bar")
exceptsqlglot.errors.ParseErrorase:
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:

importsqlglotsqlglot.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:

fromsqlglotimportselect, conditionwhere=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:

fromsqlglotimportparse_oneparse_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:

fromsqlglotimportexp, parse_oneexpression_tree=parse_one("SELECT a FROM x")
deftransformer(node):
ifisinstance(node, exp.Column) andnode.name=="a":
returnparse_one("FUN(a)")
returnnodetransformed_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:

importsqlglotfromsqlglot.optimizerimportoptimizeprint(
optimize(
sqlglot.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"<>0OR"x"."b"<>0OR"x"."c"<>0
)
AND (
"x"."a"<>0OR"x"."b"<>0OR"x"."d"<>0
) AS"_col_0"FROM"x"AS"x"WHERE
CAST("x"."z"ASDATE) = CAST('2021-02-01'ASDATE)

AST Introspection

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

fromsqlglotimportparse_oneprint(repr(parse_one("SELECT a + 1 AS z")))

(SELECTexpressions:
(ALIASthis:
(ADDthis:
(COLUMNthis:
(IDENTIFIERthis: a, quoted: False)), expression:
(LITERALthis: 1, is_string: False)), alias:
(IDENTIFIERthis: 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:

fromsqlglotimportdiff, parse_onediff(parse_one("SELECT a + b, c, d"), parse_one("SELECT c, a - b, d"))

[
Remove(expression=(ADDthis:
(COLUMNthis:
(IDENTIFIERthis: a, quoted: False)), expression:
(COLUMNthis:
(IDENTIFIERthis: b, quoted: False)))),
Insert(expression=(SUBthis:
(COLUMNthis:
(IDENTIFIERthis: a, quoted: False)), expression:
(COLUMNthis:
(IDENTIFIERthis: b, quoted: False)))),
Move(expression=(COLUMNthis:
(IDENTIFIERthis: c, quoted: False))),
Keep(source=(IDENTIFIERthis: b, quoted: False), target=(IDENTIFIERthis: b, quoted: False)),
...
]

See also: Semantic Diff for SQL.

Custom Dialects

Dialects can be added by subclassing Dialect:

fromsqlglotimportexpfromsqlglot.dialects.dialectimportDialectfromsqlglot.generatorimportGeneratorfromsqlglot.tokensimportTokenizer, TokenTypeclassCustom(Dialect):
classTokenizer(Tokenizer):
QUOTES= ["'", '"']
IDENTIFIERS= ["`"]
KEYWORDS= {
**Tokenizer.KEYWORDS,
"INT64": TokenType.BIGINT,
"FLOAT64": TokenType.DOUBLE,
}
classGenerator(Generator):
TRANSFORMS= {exp.Array: lambdaself, 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:

fromsqlglot.executorimportexecutetables= {
"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_idprice14.023.0

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