删除一行

Question

我想删除banners的任何行，如果没有相应的行banners_pp

我做的怎么办{doesn't exist}部分？

DELETE banners.* FROM banners 
LEFT JOIN banners_pp 
USING(banner_id) 
WHERE banners_pp.banner_id {doesn't exist} 

Answer 1

DELETE FROM banners 
WHERE NOT EXISTS (
    SELECT * 
    FROM banners_pp 
    WHERE banner_id = banners.banner_id 
) 

看到more细节

Answer 2

DELETE 
FROM banners 
WHERE NOT EXISTS (SElect 1 from banners_pp 
      WHERE banners_pp.banner_id = banners.banner_id) 

Answer 3

试试这个

DELETE FROM banners 
WHERE banner_id NOT IN (
SELECT banner_id 
FROM banners_pp 
) 

Answer 4

DELETE FROM banners b 
WHERE NOT EXISTS (
    SELECT * 
    FROM banners_pp bp 
    WHERE bp.banner_id = b.banner_id 
) 

Answer 5

使用WHERE banners_pp.banner_id IS NULL

在LEFT JOIN中，左表（banners）中右表中没有对应行的行（banners_pp）存在，但在右表的列中有NULL。如果在有banner_id = 2banners_pp没有进入，但在banners有banner_id = 2的条目，在连接表中的对应行可能看起来有点像这样：

| banners.banner_id | banners.foo | banners_pp.banner_id | banners_pp.bar | 
|   2   |  x  |   NULL   |  NULL |