SQL Helper

Overview

Helps write, optimize, and debug SQL queries.

When to Use

• User asks to "write a SQL query" or "optimize this query"
• Debugging slow database operations

Pagination

SELECT * FROM users ORDER BY id LIMIT 20 OFFSET 40;

Join with Aggregation

SELECT u.name, COUNT(o.id) as order_count FROM users u LEFT JOIN orders o ON u.id = o.user_id GROUP BY u.id;

Optimization Rules

• Add indexes on WHERE/JOIN columns
• Avoid SELECT * - specify columns
• Use EXPLAIN to analyze execution plan
• Optimize JOIN order (small table first)
• Add LIMIT for pagination

Anti-Patterns to Avoid

• SELECT * in production code
• Nested subqueries (use JOINs or CTEs)
• OR in WHERE clause (use IN or UNION)