Cheatsheet Pages / SQL Cheatsheet
How to upsert in SQL — INSERT ... ON CONFLICT DO UPDATE
A row may or may not exist yet — insert it if missing, update it if present, in one statement.
Every example runs against the cheatsheet's sample tables — departments(id, name), employees(id, name, dept_id, salary, manager_id, hired_on) and orders(id, emp_id, amount, ordered_on) — and was executed and verified against SQLite, so you can paste it in and get the same result.
INSERT INTO departments (id, name) VALUES (3, 'People')
ON CONFLICT(id) DO UPDATE SET name = excluded.name;
-- id=3 already exists → the department is renamed HR → People; if it didn't exist, it would be inserted
-- This is the SQLite / PostgreSQL spelling. MySQL: ON DUPLICATE KEY UPDATE name = VALUES(name) — but VALUES() is deprecated since MySQL 8.0.20; modern spelling uses a row alias: ... VALUES (3, 'People') AS new ON DUPLICATE KEY UPDATE name = new.name