Combining conditions

A WHERE clause can test more than one thing at once. Join conditions with:

• AND — both must be true
• OR — at least one must be true
• NOT — flips a condition

SELECT name FROM student WHERE form = '11A' AND score > 88;

This returns 11A students who also scored above 88.

Mixing AND and OR

When you mix AND and OR, use brackets to make the meaning clear, just like in maths:

SELECT name FROM student
WHERE form = '11B' OR score >= 95;

AND is checked before OR, so brackets remove any doubt about what you mean.

Common mistakes

• Use brackets when you mix AND and OR to make the order clear.
• NOT reverses a condition.