SQL Formatter

What Is SQL Formatting?

SQL (Structured Query Language) formatting is the process of restructuring SQL code to follow consistent styling conventions—proper indentation, line breaks, and keyword capitalization. Well-formatted SQL is easier to read, debug, and maintain. While databases do not care about whitespace or formatting, humans certainly do. A messy one-line query that works fine technically can be nearly impossible to understand or modify.

This formatter takes your SQL queries—whether copied from logs, generated by an ORM, or hastily written during debugging—and transforms them into cleanly structured, readable code. It recognizes common SQL keywords and clauses, adding appropriate line breaks and indentation to reveal the logical structure of your queries.

How the Formatter Works

The formatting algorithm processes SQL in several stages:

1. Tokenization: The input is broken into tokens (keywords, identifiers, operators, literals)
2. Pattern Recognition: Major clauses (SELECT, FROM, WHERE, etc.) are identified
3. Restructuring: Line breaks and indentation are inserted at logical points
4. Case Transformation: Keywords are converted to your preferred case

The transformation can be represented as a function that maps unformatted SQL to formatted output:

Where the function applies consistent rules based on your selected indentation style and keyword case preferences.

Formatting Rules Applied

Before and After Examples

Example 1: Simple SELECT

Before:

select id,name,email,created_at from users where status='active' and role='admin' order by created_at desc limit 10

After:

SELECT
    id,
    name,
    email,
    created_at
FROM
    users
WHERE
    status = 'active'
    AND role = 'admin'
ORDER BY
    created_at DESC
LIMIT
    10

Example 2: JOIN Query

Before:

select o.id,o.total,c.name,c.email from orders o inner join customers c on o.customer_id=c.id left join order_items oi on oi.order_id=o.id where o.status='completed'

After:

SELECT
    o.id,
    o.total,
    c.name,
    c.email
FROM
    orders o
INNER JOIN
    customers c ON o.customer_id = c.id
LEFT JOIN
    order_items oi ON oi.order_id = o.id
WHERE
    o.status = 'completed'

Why Format SQL?

Readability: Formatted SQL reveals the logical structure of queries at a glance. You can immediately see which tables are involved, what conditions apply, and how data is sorted or grouped.

Debugging: When queries produce unexpected results, formatted code makes it easier to spot logical errors, missing conditions, or incorrect joins.

Code Review: Team members reviewing SQL in pull requests or code reviews can quickly understand and verify query logic when it is properly formatted.

Documentation: Formatted queries in documentation or comments help future developers understand database interactions without deciphering wall-of-text SQL.

Consistency: Teams that follow consistent formatting standards reduce cognitive load when reading each other's code.

Formatting Style Preferences

Indentation: The debate between spaces and tabs continues in programming communities. Most SQL teams prefer spaces (typically 2 or 4) for consistent display across different editors and terminals.

Keyword Case: SQL keywords are case-insensitive, but convention matters for readability:

• UPPERCASE: The most common style, clearly distinguishes keywords from identifiers
• lowercase: Some prefer this for less visual noise, especially in longer queries
• PascalCase: Less common, used in some legacy systems

Clause Alignment: Some styles align clause keywords (SELECT, FROM, WHERE) in a column, while others indent them at different levels. This formatter uses consistent left alignment for major clauses.

SQL Keywords Recognized

The formatter recognizes and handles these common SQL keywords:

Best Practices for SQL Writing

1. Use Meaningful Aliases: Instead of single letters, use descriptive abbreviations. "ord" for orders is better than "o" for complex queries.

2. Qualify Column Names: In JOIN queries, always prefix columns with table aliases to avoid ambiguity and improve clarity.

3. Break Complex Conditions: Use parentheses and line breaks to make complex WHERE clauses readable.

4. Comment Non-Obvious Logic: Use SQL comments (-- or /* */) to explain business logic that is not self-evident.

5. Limit Line Length: Extremely long lines are hard to read. Break lines at logical points.

Integration with Development Workflows

SQL formatting integrates into development workflows in several ways:

• IDE Plugins: Most database IDEs (DataGrip, DBeaver, Azure Data Studio) have built-in formatters
• Pre-commit Hooks: Automatically format SQL files before commits
• CI/CD Pipelines: Check formatting as part of code quality gates
• Online Tools: Quick formatting for ad-hoc queries (like this tool!)

Comparison of Formatting Approaches

Frequently Asked Questions

Does formatting change how the query executes? No. SQL databases ignore whitespace and formatting. The formatted query is semantically identical to the original.

Can the formatter handle complex nested queries? This formatter handles basic nesting, but extremely complex queries with deep nesting may require manual adjustment for optimal readability.

What about stored procedures or PL/SQL? This tool focuses on DML statements (SELECT, INSERT, UPDATE, DELETE). Procedural SQL with IF/ELSE, loops, and variables may not format optimally.

Is my SQL sent to a server? No. All formatting happens entirely in your browser using JavaScript. Your queries never leave your device.

Why do some formatting tools produce different output? There is no universal SQL formatting standard. Different tools apply different rules. Choose a style that works for your team and apply it consistently.

Limitations

This formatter is designed for common SQL patterns and may not handle all edge cases perfectly:

• Complex nested subqueries may need manual adjustment
• Database-specific syntax (MySQL, PostgreSQL, SQL Server extensions) may not be fully recognized
• String literals containing SQL keywords are handled conservatively
• Procedural SQL (stored procedures, functions) is not specifically supported
• Very long queries may need manual optimization for readability

For production code or complex queries, consider using database-specific formatters or IDE plugins that understand your exact SQL dialect.