Lesson 3 / 37 · Conditions and NULL

AND means every condition must be TRUE

Each condition gets its own ✓ ✗ column. A row survives only when every column shows ✓. The list above the grid tells you which condition failed first for each dropped row. An ∅ means the test was unknown; the NULL lessons that follow explain it.

The query

SELECT id, status, amount
FROM orders
WHERE status = 'paid' AND amount > 10

Try amount > 50: 8 rows pass, and the amount test now drops 4 rows, one of them ∅.

Next: AND is evaluated before OR · All lessons