INSERT, UPDATE and DELETE in MySQL with Examples

Reading data is only half the job — INSERT, UPDATE, and DELETE are how data enters and changes in your tables. One golden rule runs through all of them: never forget the WHERE clause.

Key Points

• INSERT INTO t (col1, col2) VALUES (v1, v2); — multiple rows in one statement with comma-separated tuples
• INSERT INTO t SELECT … copies data between tables
• UPDATE t SET status='shipped' WHERE id=101; — WHERE is critical
• DELETE FROM t WHERE created_at < '2024-01-01'; removes matching rows
• Upsert: INSERT … ON DUPLICATE KEY UPDATE handles insert-or-update logic
• Safety net: run SELECT with the same WHERE first, and use transactions