mysql - DELETE FROM x LEFT JOIN y WHERE x.a IS NOT NULL IN 表 y

Question

如何删除A表中B表中不存在的记录？

我尝试过这个:

DELETE FROM
    x
LEFT JOIN
    y
ON
    x.image_hash IS NOT NULL IN y

Answer 1

使用EXISTS或NOT EXISTS适当的条款。

DELETE FROM x WHERE <NOT> EXISTS (SELECT 1 FROM y WHERE y.<something> = x.<some_column> AND <some more conditions>