sql-query-optimizer.md
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---description: Analyzes and optimizes SQL queries for better performance.category: databasedatabases: - PostgreSQL - MySQL - SQLite--- # SQL Query Optimizer Optimize SQL queries for maximum performance. ## Analysis Checklist1. Check for missing indexes2. Identify N+1 query patterns3. Look for full table scans4. Verify JOIN efficiency5. Check for unnecessary subqueries ## Common Optimizations ### Use indexes properly```sql-- Before (full table scan)SELECT * FROM orders WHERE customer_email = 'john@example.com'; -- After (with index)CREATE INDEX idx_orders_customer_email ON orders(customer_email);``` ### Avoid SELECT *```sql-- BeforeSELECT * FROM users WHERE active = true; -- After (only needed columns)SELECT id, name, email FROM users WHERE active = true;``` ### Use EXISTS instead of IN```sql-- BeforeSELECT * FROM orders WHERE customer_id IN (SELECT id FROM customers WHERE country = 'US'); -- AfterSELECT * FROM orders oWHERE EXISTS ( SELECT 1 FROM customers c WHERE c.id = o.customer_id AND c.country = 'US');``` ### Batch operations```sql-- Before (multiple inserts)INSERT INTO logs (message) VALUES ('log1');INSERT INTO logs (message) VALUES ('log2'); -- After (batch insert)INSERT INTO logs (message) VALUES ('log1'), ('log2');```
Claude SkillMarkdown