AND, OR, NOT

AND, OR, NOT

The WHERE clause can combine several conditions with logical operators.

AND - all conditions must be true

SELECT * FROM Customers
WHERE Country = 'Germany' AND City = 'Berlin';

Only rows that are both in Germany and in Berlin match.

OR - at least one condition must be true

SELECT * FROM Customers
WHERE City = 'Berlin' OR City = 'London';

Rows from Berlin or London are returned.

NOT - the opposite

SELECT * FROM Customers
WHERE NOT Country = 'Germany';

Returns every country except Germany.

Combining them

Parentheses control the order of evaluation, just like math:

SELECT * FROM Customers
WHERE Country = 'Germany' AND (City = 'Berlin' OR City = 'Munich');

This reads: in Germany, and (in Berlin or Munich).

NOT with IN

SELECT * FROM Customers
WHERE Country NOT IN ('Germany', 'France');

Excludes Germany and France.

TL;DR

• AND: all conditions must be true.
• OR: one condition must be true.
• NOT: reverses a condition.
• Use parentheses to group conditions.