Optimize your SQL queries for better performance. Essential techniques for handling large datasets.

Use Indexes Wisely

-- Create index on frequently queried columns

CREATE INDEX idx_customer_email ON customers(email);

CREATE INDEX idx_order_date ON orders(order_date);

Avoid SELECT *

-- Bad

SELECT * FROM orders;

-- Good

SELECT id, customer_id, total, order_date FROM orders;

Use EXPLAIN

EXPLAIN SELECT * FROM orders WHERE customer_id = 123;

Optimize JOINs

-- Ensure JOIN columns are indexed

-- Join smaller table to larger table

-- Use INNER JOIN when possible

Limit Results

SELECT * FROM logs ORDER BY created_at DESC LIMIT 100;

Avoid Functions on Indexed Columns

-- Bad (can't use index)

SELECT * FROM orders WHERE YEAR(order_date) = 2025;

-- Good (uses index)

SELECT * FROM orders WHERE order_date >= '2025-01-01' AND order_date < '2026-01-01';

Use EXISTS Instead of IN for Large Sets

SELECT * FROM products p

WHERE EXISTS (SELECT 1 FROM order_items oi WHERE oi.product_id = p.id);

Batch Large Operations

-- Instead of one huge DELETE

DELETE FROM logs WHERE created_at < '2024-01-01' LIMIT 10000;

Optimize with AI2sql

AI2sql generates optimized queries automatically.