# SQLFluff — Modular SQL Linter and Auto-Formatter

> A configurable SQL linter and formatter supporting over 20 SQL dialects, designed to enforce style rules and catch errors in data pipelines.

## Install

Save in your project root:

# SQLFluff — Modular SQL Linter and Auto-Formatter

## Quick Use
```bash
pip install sqlfluff
sqlfluff lint my_query.sql --dialect postgres
sqlfluff fix my_query.sql --dialect postgres
```

## Introduction
SQLFluff is an open-source SQL linter that brings the same code-quality discipline to SQL that ESLint brings to JavaScript. It parses, analyzes, and auto-fixes SQL files across many dialects, helping data teams enforce consistent formatting in version-controlled analytics repos.

## What SQLFluff Does
- Lints SQL files against configurable rules for style and correctness
- Auto-fixes violations with a single command
- Supports 20+ dialects including PostgreSQL, BigQuery, Snowflake, Redshift, and SparkSQL
- Integrates with CI pipelines, pre-commit hooks, and dbt projects
- Provides a templating layer to handle Jinja and dbt macros

## Architecture Overview
SQLFluff parses SQL into an abstract syntax tree using dialect-specific grammars. Each rule inspects tree nodes and emits lint violations with optional fix patches. The fix engine applies non-conflicting patches in a single pass; conflicting fixes require multiple passes. A plugin system allows third-party rules.

## Self-Hosting & Configuration
- Install via pip: `pip install sqlfluff`
- Configure with `.sqlfluff` file in your project root
- Set dialect: `[sqlfluff] dialect = bigquery`
- Exclude rules: `[sqlfluff:rules] exclude_rules = L011,L031`
- Integrate with pre-commit by adding the sqlfluff hook entry

## Key Features
- Over 60 built-in lint rules covering indentation, aliasing, joins, and naming
- Dialect-aware parsing handles syntax differences correctly
- Jinja and dbt templating support for analytics SQL
- Configurable via TOML or INI-style config files
- Plugin architecture for custom rules

## Comparison with Similar Tools
- **sqlfmt** — opinionated formatter with fewer configuration options
- **pg_format** — PostgreSQL-only, no lint rules
- **sql-formatter** — JavaScript library focused on pretty-printing, no linting
- **dbt SQLFluff plugin** — extends SQLFluff with dbt-aware templating
- **SonarQube SQL** — enterprise tool with broader scope but commercial licensing

## FAQ
**Q: Does SQLFluff work with dbt projects?**
A: Yes. It has built-in dbt templating support and can parse Jinja macros before linting.

**Q: Can I use SQLFluff in CI?**
A: Yes. Run `sqlfluff lint --format github-annotation` for inline PR comments in GitHub Actions.

**Q: How do I ignore a specific violation?**
A: Add `-- noqa: L042` as an inline comment on the offending line.

**Q: Does it support BigQuery and Snowflake?**
A: Yes, both are first-class supported dialects with dedicated grammar files.

## Sources
- https://github.com/sqlfluff/sqlfluff
- https://docs.sqlfluff.com/

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Source: https://tokrepo.com/en/workflows/asset-ae7d585b
Author: AI Open Source