sqltree

sqltree is an experimental parser for SQL, providing a syntax tree for SQL queries. Possible use cases include:

• Static analysis (for example, to validate column names)
• Translating queries to another SQL dialect
• Autoformatting

sqltree can parse queries:

$ python -m sqltree "SELECT * FROM x WHERE x = 3"
Select(select_exprs=[SelectExpr(expr=Star(), alias=None)], table=Identifier(text='x'), conditions=BinOp(left=Identifier(text='x'), op=Punctuation(text='='), right=IntegerLiteral(value=3)))

And format them:

$  python -m sqltree.formatter "SELECT * from x where x=3"
SELECT *
FROM x
WHERE x = 3

SQL is a big language with a complicated grammar that varies significantly between database vendors. sqltree is designed to be flexible enough to parse the full syntax supported by different databases, but I am prioritizing constructs used in my use cases for the parser. So far, that has meant a focus on parsing MySQL 8 queries. Further syntax will be added as I have time.

Features

Useful features of sqltree include:

Placeholder support

sqltree supports placeholders such as %s or ? in various positions in the query, so that queries using such placeholders can be formatted and analyzed.

$ python -m sqltree.formatter 'select * from x where y = 3 %(limit)s'
SELECT *
FROM x
WHERE y = 3
%(limit)s

Better error messages

sqltree's handwritten parser often produces better error messages than MySQL itself. For example:

$ mysql
mysql> show replicca status;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'replicca status' at line 1
$ python -m sqltree 'show replicca status'
Unexpected 'replicca' (expected one of REPLICA, SLAVE, REPLICAS, TABLES, TABLE, TRIGGERS, VARIABLES, STATUS, COUNT, WARNINGS, ERRORS, COLUMNS, FIELDS, INDEX, INDEXES, KEYS)
0: show replicca status
        ^^^^^^^^

API

• sqltree.sqltree: parse a SQL query and return the parse tree. See sqltree.parser for the possible parse nodes.
• sqltree.formatter.format: reformat a SQL query.
• sqltree.tools.get_tables: get the tables referenced in a SQL query.

More detailed documentation to follow.

Requirements

sqltree runs on Python 3.6 and up and it has no dependencies.

Using the fixit rule

sqltree embeds a fixit rule for formatting SQL. Here is how to use it:

• Install fixit if you don't have it yet
  • pip install fixit
  • python -m fixit.cli.init_config
• Run python -m fixit.cli.apply_fix --rules sqltree.fixit.SqlFormatRule path/to/your/code

Changelog

Version 0.1.0 (June 13, 2022)

• Initial release