MYSQL存儲過程刪除

Question

我有存儲過程：

BEGIN
SELECT @id_for_del := ful.social_id
FROM facebook_users_likes ful 
where
(select count(*) from facebook_users fu where fu.social_id = ful.social_id) = 0;
IF NOT @id_for_del IS NULL
THEN 
DELETE from facebook_users_likes WHERE social_id = @id_for_del;
END IF;
END

Select返回46,000行，但每個執行存儲過程僅刪除一行。 那么，如何一次刪除所有46 000行？

Answer 1

這是將select直接轉換為delete翻譯：

DELETE FROM facebook_users_likes ful 
WHERE (select count(*) from facebook_users fu where fu.social_id = ful.social_id) = 0;

在這種情況下使用not exists會更有效：

DELETE FROM facebook_users_likes ful 
WHERE NOT EXISTS (select 1 from facebook_users fu where fu.social_id = ful.social_id);

如果您在facebook_users(social_id)上具有索引，則尤其如此。