MySQL更新更新所有行？

Question

I'm trying to create an sql query that will check through a table and if it cannot find a row in a different table with the same id then it modifies a field in the original table.

UPDATE book SET reserved = 'N' WHERE not exists ( SELECT * FROM reservedbooks WHERE book = $row[bookID]

I'm running this in a loop in php where $row[bookID] represents all the book ids. my problem is that when this finds a match it sets all of 'reserved' columns values to 'N', not just the one it cant find a value for.

any help would be greatly appreciated :)

Answer 1

用这个：

UPDATE book SET reserved = 'N' WHERE id not in ( SELECT id FROM reservedbooks WHERE book = $row[bookID]