Filtering Rows with WHERE | Learn SQL Visual

WHERE Keeps Matching Rows

WHERE keeps only the rows that satisfy a condition. With WHERE city = 'Tokyo', the rows whose city is Tokyo remain and the rest drop out. WHERE changes which rows remain, never which columns come back.

SELECT * FROM customers WHERE city = 'Tokyo' returns how many rows?

CHECK IT

SELECT *
FROM customers
WHERE …

Matches the condition (kept)abcDoesn't match (dropped)

customers6 of 6 rows kept

id	name	city	referred_by
1	Alice	Tokyo	NULL
2	Bob	Osaka	1
3	Carol	Tokyo	2
4	Dave	Osaka	1
5	Erin	Nagoya	NULL
6	Frank	NULL	3

WHERE keeps only the rows that match a condition. Before you write one, every row stays.