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Modular SQL Linting for Humans

Project description


The SQL Linter for humans

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Bored of not having a good SQL linter that works with whichever dialect you're working with? SQLFluff is an extensible and modular linter designed to help you write good SQL and catch errors before it hits your database. SQLFluff can auto-fix most linting errors too.

Getting Started

To get started, install the package and run sqlfluff lint or sqlfluff fix.

$ pip install sqlfluff
$ echo "  SELECT a  +  b FROM tbl;  " > test.sql
$ sqlfluff lint test.sql
== [test.sql] FAIL
L:   1 | P:   1 | L003 | Single indentation uses a number of spaces not a multiple of 4
L:   1 | P:  14 | L006 | Operators should be surrounded by a single space unless at the start/end of a line
L:   1 | P:  27 | L001 | Unnecessary trailing whitespace

You can also have a play using SQLFluff online.

For full CLI usage and rules reference, see the docs.


For full documentation visit


SQLFluff is still in an open alpha phase - expect the tool to change significantly over the coming months, and expect potentially non-backward compatible api changes to happen at any point. If you'd like to help please consider contributing.

  • 0.4.x (ongoing development) will fully support dbt packages and macros with significant speed improvements and new rules.
  • 0.3.x dropped support for python 2.7 and 3.4, and reworked the handling of indentation linting in a potentially not backward compatible way.
  • 0.2.x added templating support and a big restructure of rules and changed how users might interact with sqlfluff on templated code.
  • 0.1.x involved a major re-write of the parser, completely changing the behaviour of the tool with respect to complex parsing.

SQLFluff on Slack

We have a fast-growing community on Slack, come and join us!


There's lots to do in this project, and we're just getting started. If you want to understand more about the architecture of SQLFluff, you can find more here.

If you'd like to contribute, check out the open issues on GitHub. You can also see the guide to contributing.


All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.



  • Public API to enable people to import sqlfluff as a python module and call parse, lint and fix within their own projects. See the docs for more information. (#501)
  • The ability to use dbt as a templating engine directly allowing richer and more accurate linting around dbt macros (and packages related to dbt). For more info see the docs. (#508)
  • Support for modulo (%) operator. (#447)
  • A limit in the internal fix routines to catch any infinite loops. (#494)
  • Added the .istype() method on segments to more intelligently deal with type matching in rules when inheritance is at play.
  • Added the ability for the user to add their own rules when interacting with the Linter directly using user_rules.
  • Added L034 'Fields should be stated before aggregates / window functions' per dbt coding convenventions (#495)
  • Templating tags, such as {{ variables }}, {# comments #} and {% loops %} (in jinja) now have placeholders in the parsed structure. Rule L003 (indentation), also now respects these placeholders so that their indentation is linted accordingly. For loop or block tags, they also generate an Indent and Dedent tag accordingly (which can be enabled or disabled) with a configuration value so that indentation around these functions can be linted accordingly. (#541)
  • MyPy type linting into a large proportion of the core library. (#526, #580)
  • Config values specific to a file can now be defined using a comment line starting with -- sqlfluff:. (#541)
  • Added documentation for --noqa: use in rules. (#552)
  • Added pre-commit hooks for lint and fix. (#576)
  • Added a fix routine for Rule L019 (comma placement). (#575)
  • Added Rule L031 to enforce "avoid using alias in the FROM/JOIN clauses" from the dbt coding conventions. (#473, #479)
  • Added Rule L032 to enforce "do not use USING" from the dbt coding conventions. (#487)
  • Added Rule L033 to enforce "prefer UNION ALL to UNION *" from the dbt coding conventions. (#489)
  • Added Rule L034 to enforce "fields should be stated before aggregate/window functions" from the dbt coding conventions. (#495)
  • Adopted the black coding style. (#485)
  • Added validation and documentation for rule configuration options. (#462)
  • Added documentation for which rules are fixable. (#594)
  • Added EPOCH keyword for postgres dialect. (#522)
  • Added column index identifier in snowflake dialect. (#458)
  • Added USE statement to the snowflake dialect. (#537)
  • Added CODE_OF_CONDUCT to the project. (#471)
  • Added ISNULL and NOTNULL keywords to ansi dialect. (#441)
  • Added support for python 3.9. (#482)
  • Added requirements_dev.txt for local testing/linting. (#500)
  • Added CLI option --disregard-sqlfluffignores to allow direct linting of files in the .sqlfluffignore. (#486)
  • Added dbt incremental macro. (#363)
  • Added links to cockroachlabs expression grammars in ansi dialect. (#592)
  • Added favicon to the docs website. (#589)


  • Big refactor of logging internally. Linter is now decoupled from logging so that it can be imported directly by subprojects without needing to worry about weird output or without the log handing getting in the way of your project. (#460)
  • Linting errors in the final file are now reported with their position in the source file rather than in the templated file. This means when using sqlfluff as a plugabble library within an IDE, the references match the file which is being edited. (#541)
  • Created new Github Organisation ( and migrated from to (#444)
  • Changed the handling of * and a.b.* expressions to have their own expressions. Any dependencies on this structure downstream will be broken. This also fixes the linting of both kinds of expressions with regard to L013 and L025. (#454)
  • Refactor of L022 to handle poorly formatted CTEs better. (#494)
  • Internally added an EphemeralSegment to aid with parsing efficiency without altering the end structure of the query. (#491)
  • Split ObjectReference into ColumnReference and TableReference for more useful API access to the underlying structure. (#504)
  • KeywordSegment and the new SymbolSegment both now inherit from _ProtoKeywordSegment which allows symbols to match in a very similar way to keywords without later appearing with the type of keyword. (#504)
  • Introduced the Parser class to parse a lexed query rather than relying on users to instantiate a FileSegment directly. As a result the FileSegment has been moved from the core parser directly into the dialects. Users can refer to it via the get_root_segment() method of a dialect. (#510)
  • Several perfomance improvements through removing unused functionality, sensible caching and optimising loops within functions. (#526)
  • Split up rule tests into separate yml files. (#553)
  • Allow escaped quotes in strings. (#557)
  • Fixed ESCAPE parsing in LIKE clause. (#566)
  • Fixed parsing of complex BETWEEN statements. (#498)
  • Fixed BigQuery EXCEPT clause parsing. (#472)
  • Fixed Rule L022 to respect leading comma configuration. (#455)
  • Improved instructions on adding a virtual environment in the README. (#457)
  • Improved documentation for passing CLI defaults in .sqlfluff. (#452)
  • Fix bug with templated blocks + capitalisation_policy = lower. (#477)
  • Fix array accessors in snowflake dialect. (#442)
  • Color logging warnings red. (#497)
  • Allow whitespace before a shorthand cast. (#544)
  • Silenced warnings when fixing from stdin. (#522)
  • Allow an underscore as the first char in a semi structured element key. (#596)
  • Fix PostFunctionGrammar in the Snowflake dialect which was causing strange behaviour in L012. (#619)


  • Dropped support for python 3.5. (#482)
  • From the CLI, the --no-safety option has been removed, the default is now that all enabled rules will be fixed. (#583)
  • Removed BaseSegment.grammar, BaseSegment._match_grammar() and BaseSegment._parse_grammar() instead preferring references directly to BaseSegment.match_grammar and BaseSegment.parse_grammar. (#509)
  • Removed EmptySegmentGrammar and replaced with better non-code handling in the FileSegment itself. (#509)
  • Remove the ContainsOnly grammar as it remained only as an anti-pattern. (#509)
  • Removed the expected_string() functionality from grammars and segments (#509) as it was poorly supported.
  • Removed BaseSegment.as_optional() as now this functionality happens mostly in grammars (including Ref). (#509)
  • Removed ColumnExpressionSegment in favour of ColumnReference. (#512)
  • Removed the LambdaSegment feature, instead replacing with an internal to the grammar module called NonCodeMatcher. (#512)
  • Case sensitivity as a feature for segment matching has been removed as not required for existing dialects. (#517)
  • Dependency on difflib or cdifflib, by relying on source mapping instead to apply fixes. (#541)

[0.3.6] - 2020-09-24


  • sqlfluff dialects command to get a readout of available dialects [+ associated docs].
  • More helpful error messages when trying to run in Python2.
  • Window functions now parse with IGNORE/RESPECT NULLS.
  • Parsing of current_timestamp and similar functions. Thanks @dmateusp.
  • Snowflake QUALIFY clause.


  • Respect user config directories. Thanks @sethwoodworth.
  • Fix incorrect reporting of L013 with *. Thanks @dmateusp.
  • Fix incorrect reporting of L027 with column aliases. Thanks @pwildenhain.
  • Simplification of application of fixes and correction of a case where fixes could be depleted. Thanks @NiallRees.
  • Fix functions with a similar structure to SUBSTRING.
  • Refactor BigQuery REPLACE and EXCEPT clauses.
  • Bigquery date parts corrected.
  • Snowflake array accessors.
  • Psotgres NOTNULL and ISNULL.
  • Bugfix in snowflake for keywords used in semistructured queries.
  • Nested WITH statements now parse.
  • Performance improvements in the fix command.
  • Numeric literals starting with a decimal now parse.
  • Refactor the jinja templater.

[0.3.5] - 2020-08-03


  • Patterns and Anti-patterns in documentation. Thanks @flpezet.
  • Functions in GROUP BY. Thanks @flpezet.


  • Deep bugfixes in the parser to handle simple matching better for a few edge cases. Also added some logging deeper in the parser.
  • Added in the SelectableGrammar and some related segments to make it easier to refer to select-like things in other grammars.
  • Fixes to CASE statement parsing. Thanks @azhard.
  • Fix to snowflake SAMPLE implementation. Thanks @rkm3.
  • Numerous docs fixes. Thanks @SimonStJG, @flpezet, @s-pace, @nolanbconaway.

[0.3.4] - 2020-05-13


  • Implementation of the bigquery CREATE MODEL syntax. Thanks @barrywhart.
  • Bugfixes for:
    • Edge cases for L006
    • False alarms on L025
    • FOR keyword in bigquery SYSTEM_TIME syntax.

[0.3.3] - 2020-05-11


  • Added the --nofail option to parse and lint commands to assist rollout.
  • Added the --version option to complement the version option already available on the cli.
  • Parsing for ALTER TABLE.
  • Warning for unset dialects when getting parsing errors.
  • Configurable line lengths for output.

[0.3.2] - 2020-05-08


  • Support for the Teradata dialect. Thanks @Katzmann1983!
  • A much more detailed getting started guide in the docs.
  • For the parse command, added the --profiler and --bench options to help debugging performance issues.
  • Support for the do command in the jinja templater.
  • Proper parsing of the concatenate operator (||).
  • Proper indent handling of closing brackets.
  • Logging and benchmarking of parse performance as part of the CI pipeline.
  • Parsing of object references with defaults like my_db..my_table.
  • Support for the INTERVAL '4 days' style interval expression.
  • Configurable trailing or leading comma linting.
  • Configurable indentation for JOIN clauses.
  • Rules now have their own logging interface to improve debugging ability.
  • Snowflake and Postgres dialects.
  • Support for a .sqlfluffignore file to ignore certain paths.
  • More generic interfaces for managing keywords in dialects, including set interfaces for managing and creating keywords and the Ref.keyword() method to refer to them, and the ability to refer directly to keyword names in most grammars using strings directly. Includes SegmentGenerator objects to bind dialect objects at runtime from sets. Thanks @Katzmann1983!
  • Rule L029 for using unreserved keywords as variable names.
  • The jinja templater now allows macros loaded from files, and the hydration of variables ending in _path in the config files.
  • JSON operators and the DISTINCT ON () syntax for the postgres dialect.


  • Refactor of whitespace and non-code handling so that segments are less greedy and default to not holding whitespace on ends. This allows more consistent linting rule application.
  • Change config file reading to case-sensitive to support case sensitivity in jinja templating.
  • Non-string values (including lists) now function in the python and jinja templating libraries.
  • Validation of the match results of grammars has been reduced. In production cases the validation will still be done, but only on parse and not on match.
  • At low verbosities, python level logging is also reduced.
  • Some matcher rules in the parser can now be classified as simple which allows them to shortcut some of the matching routines.
  • Yaml output now double quotes values with newlines or tab characters.
  • Better handling on hanging and closing indents when linting rule L003.
  • More capable handline of multi-line comments so that indentation and line length parsing works. This involves some deep changes to the lexer.
  • Getting violations from the linter now automatically takes into account of ignore rules and filters.
  • Several bugfixes, including catching potential infinite regress during fixing of files, if one fix would re-introduce a problem with another.
  • Behaviour of the Bracketed grammar has been changed to treat its content as a Sequence rather than a OneOf.
  • Move to SandboxedEnvironment rather than Environment for jinja templating for security.
  • Improve reporting of templating issues, especially for the jinja templater so that missing variables are rendered as blanks, but still reported as templating violations.

[0.3.1] - 2020-02-17


  • Support for a.b.* on top of a.* in select target expressions.

[0.3.0] - 2020-02-15


  • Deprecated python 2.7 and python 3.4 which are now both past their maintenance horizon. The 0.2.x branch will remain available for continued development for these versions.
  • Rule L003 is now significantly smarter in linting indentation with support for hanging indents and comparison to the most recent line which doesn't have an error. The old (more simple) functionality of directly checking whether an indent was a multiple of a preset value has been removed.
  • Fixed the "inconsistent" bug in L010. Thanks @nolanbconaway.
  • Updated logging of parsing and lexing errors to have more useful error codes.
  • Changed parsing of expressions to favour functions over identifiers to fix the expression bug.
  • Fixed the "inconsistent" bug in L010. Thanks @nolanbconaway.
  • Moved where the SELECT keyword is parsed within a select statement, so that it belongs as part of the newly renamed select_clause (renamed from previously select_target_group).
  • Clarified handling of the type and name properties of the BaseSegment class and its children. name should be specific to a particular kind of segment, and type should express a wider group. Handling of the newline, whitespace and comma segments has been updated so that we use the type property for most use cases rather than name.


  • Meta segments for indicating where things can be present in the parsed tree. This is mostly illustrated using the Indent and Dedent segments used for indicating the position of theoretical indents in the structure. Several helper functions have been added across the codebase to handle this increase in the kinds of segments which might be encountered by various grammars.
  • Rule L016 has been added to lint long lines. In the fix phase of this rule, there is enough logic to try and reconstruct a sensible place for line breaks as re-flow the query. This will likely need further work and may still encounter places where it doesn't fix all errors but should be able to deal with the majority of simple cases.
  • BigQuery dialect, initially just for appropriate quoting.
  • Added parsing of DDL statements such as COMMIT, DROP, GRANT, REVOKE and ROLLBACK. Thanks @barrywhart.
  • --format option to the parse command that allows a yaml output. This is mostly to make test writing easier in the development process but might also be useful for other things.
  • Parsing of set operations like UNION.
  • Support for the diff-cover tool. Thanks @barrywhart.
  • Enabled the fix command while using stdin. Thanks @nolanbconaway.
  • Rule to detect incorrect use of DISTINCT. Thanks @barrywhart.
  • Security fixes from DeepCover. Thanks @sanketsaurav.
  • Automatic fix testing, to help support the newer more complicated rules.
  • Interval literals
  • Support for the source macro from dbt. Thanks @Dandandan
  • Support for functions with spaces between the function name and the brackets and a linting rule L017 to catch this.
  • Efficiency cache for faster pruning of the parse tree.
  • Parsing of array notation as using in BigQuery and Postgres.
  • Enable the ignore parameter on linting and fixing commands to ignore particular kinds of violations.

[0.2.4] - 2019-12-06


  • A --code-only option to the parse command to spit out a more simplified output with only the code elements.
  • Rules can now optionally override the description of the violation and pass that back via the LintingResult.


  • Bugfix, correct missing files in install_requires section.
  • Better parsing of the not equal operator.
  • Added more exclusions to identifier reserved words to fix cross joins.
  • At verbosity levels 2 or above, the root config is printed and then any diffs to that for specific files are also printed.
  • Linting and parsing of directories now reports files in alphabetical order. Thanks @barrywhart.
  • Better python 2.7 stability. Thanks @barrywhart.
  • Fixing parsing of IN/NOT IN and IS/IS NOT.

[0.2.3] - 2019-12-02


  • Bugfix, default config not included.

[0.2.2] - 2019-12-02


  • Tweek rule L005 to report more sensibly with newlines.
  • Rework testing of rules to be more modular.
  • Fix a config file bug if no root config file was present for some values. Thanks @barrywhart.
  • Lexing rules are now part of the dialect rather than a global so that they can be overriden by other dialects when we get to that stage.

[0.2.0] - 2019-12-01


  • Templating support (jinja2, python or raw).
    • Variables + Macros.
    • The fix command is also sensitive to fixing over templates and will skip certain fixes if it feels that it's conflicted.
  • Config file support, including specifying context for the templater.
  • Documentation via Sphinx and readthedocs.
    • Including a guide on the role of SQL in the real world. Assisted by @barrywhart.
  • Documentation LINTING (given we're a linting project) introduced in CI.
  • Reimplemented L006 & L007 which lint whitespace around operators.
  • Ability to configure rule behaviour direclty from the config file.
  • Implemented L010 to lint capitalisation of keywords.
  • Allow casting in the parser using the :: operator.
  • Implemented GROUP BYand LIMIT.
  • Added ORDER BY using indexes and expressions.
  • Added parsing of CASE statements.
  • Support for window/aggregate functions.
  • Added linting and parsing of alias expressions.


  • Fixed a bug which could cause potential infinite recursion in configuration
  • Changed how negative literals are handled, so that they're now a compound segment rather than being identified at the lexing stage. This is to allow the parser to resolve the potential ambiguity.
  • Restructure of rule definitions to be more streamlined and also enable autodocumentation. This includes a more complete RuleSet class which now holds the filtering code.
  • Corrected logging in fix mode not to duplicate the reporting of errors.
  • Now allows insert statements with a nested with clause.
  • Fixed verbose logging during parsing.
  • Allow the Bracketed grammar to optionally match empty brackets using the optional keyword.

[0.1.5] - 2019-11-11


  • Python 3.8 Support!


  • Moved some of the responsibility for formatted logging into the linter to mean that we can log progressively in large directories.
  • Fixed a bug in the grammar where one of the return values was messed up.

[0.1.4] - 2019-11-10


  • Added a --exclude-rules argument to most of the commands to allow rule users to exclude specific subset of rules, by @sumitkumar1209
  • Added lexing for !=, ~ and ::.
  • Added a new common segment: LambdaSegment which allows matching based on arbitrary functions which can be applied to segments.
  • Recursive Expressions for both arithmetic and functions, based heavily off the grammar provided by the guys at CockroachDB.
  • An Anything grammar, useful in matching rather than in parsing to match anything.


  • Complete rewrite of the bracket counting functions, using some centralised class methods on the BaseGrammar class to support common matching features across multiple grammars. In particular this affects the Delimited grammar which is now much simpler but does also require slightly more liberal use of terminators to match effectively.
  • Rather than passing around multiple variables during parsing and matching, there is now a ParseContext object which contains things like the dialect and various depths. This simplifies the parsing and matching code significantly.
  • Bracket referencing is now done from the dialect directly, rather than in individual Grammars (except the Bracketed grammar, which still implements it directly). This takes out some originally duplicated code.
  • Corrected the parsing of ordering keywords in and ORDER BY clause.


  • Removed the bracket_sensitive_forward_match method from the BaseGrammar. It was ugly and not flexible enough. It's been replaced by a suite of methods as described above.

[0.1.3] - 2019-10-30


  • Tweak to the L001 rule so that it doesn't crash the whole thing.

[0.1.2] - 2019-10-30


  • Fixed the errors raised by the lexer.

[0.1.1] - 2019-10-30


  • Fixed which modules from sqlfluff are installed in the This affects the version command.

[0.1.0] - 2019-10-29


  • Big Rewrite - some loss in functionality might be apparent compared to pre-0.1.0. Please submit any major problems as issues on github
  • Changed unicode handling for better escape codes in python 2. Thanks @mrshu
  • BIG rewrite of the parser, completely new architecture. This introduces breaking changes and some loss of functionality while we catch up.
    • In particular, matches now return partial matches to speed up parsing.
    • The Delimited matcher has had a significant re-write with a major speedup and broken the dependency on Sequence.
    • Rewrite of StartsWith and Sequence to use partial matches properly.
    • Different treatment of numeric literals.
    • Both Bracketed and Delimited respect bracket counting.
    • MASSIVE rewrite of Bracketed.
  • Grammars now have timers.
  • Joins properly parsing,
  • Rewrite of logging to selectively output commands at different levels of verbosity. This uses the verbosity_logger method.
  • Added a command line sqlfluff parse option which runs just the parsing step of the process to better understand how a file is being parsed. This also has options to configure how deep we recurse.
  • Complete Re-write of the rules section, implementing new crawlers which implement the linting rules. Now with inbuilt fixers in them.
  • Old rules removed and re implemented so we now have parity with the old rule sets.
  • Moved to using Ref mostly within the core grammar so that we can have recursion.
  • Used recursion to do a first implementation of arithmetic parsing. Including a test for it.
  • Moved the main grammar into a seperate dialect and renamed source and test files accordingly.
  • Moved to file-based tests for the ansi dialect to make it easier to test using the tool directly.
  • As part of file tests - expected outcomes are now encoded in yaml to make it easier to write new tests.
  • Vastly improved readability and debugging potential of the _match logging.
  • Added support for windows line endings in the lexer.

[0.0.7] - 2018-11-19


  • Added a sqlfluff fix as a command to implement auto-fixing of linting errors. For now only L001 is implemented as a rule that can fix things.
  • Added a rules command to introspect the available rules.
  • Updated the cli table function to use the testwrap library and also deal a lot better with longer values.
  • Added a --rules argument to most of the commands to allow rule users to focus their search on a specific subset of rules.


  • Refactor the cli tests to use the click CliRunner. Much faster

[0.0.6] - 2018-11-15


  • Number matching


  • Fixed operator parsing and linting (including allowing the exception of (*))

[0.0.5] - 2018-11-15


  • Much better documentation including the


  • Fixed comma parsing and linting

[0.0.4] - 2018-11-14


  • Added operator regexes
  • Added a priority for matchers to resolve some ambiguity
  • Added tests for operator regexes
  • Added ability to initialise the memory in rules

[0.0.3] - 2018-11-14


  • Refactor of rules to allow rules with memory
  • Adding comma linting rules (correcting the single character matchers)
  • Adding mixed indentation linting rules
  • Integration with CircleCI, CodeCov and lots of badges


  • Changed import of version information to fix bug with importing config.ini
  • Added basic violations/file reporting for some verbosities
  • Refactor of rules to simplify definition
  • Refactor of color cli output to make it more reusable

[0.0.2] - 2018-11-09


  • Longer project description
  • Proper exit codes
  • colorama for colored output


  • Significant CLI changes
  • Much improved output from CLI

[0.0.1] - 2018-11-07


  • Initial Commit! - VERY ALPHA
  • Restructure into package layout
  • Adding Tox and Pytest so that they work

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