UPDATE and DELETE | Learn SQL

Filter the Rows to Change

UPDATE and DELETE use WHERE to select affected rows. UPDATE changes values and DELETE removes rows. Without WHERE, every row is targeted, so inspect the target with the same SELECT condition first.

GOAL

Predict affected rows before a change.

What does UPDATE without WHERE target?

CHECK IT

SELECT id, name, city
FROM customers
WHERE id = 2

更新対象の行 / UPDATE target1 row

id	name	city
2	Bob	Osaka

UPDATE changes values in rows matched by WHERE. Only Bob at id 2 is targeted, and city is still Osaka.