How to remove duplicate values from a result — SELECT DISTINCT

A column repeats the same values across rows and you want each value once.

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.

SELECT DISTINCT dept_id FROM employees;
-- 1 / 2 / 3 / NULL (Grace has no department; NULL counts as a value here)

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