Question

我有以下MANY_2_MANY表users_categories：

user_id | category_id
----------------------
   1    |  138
   1    |  1262
   2    |  1262
   3    |  1262

对于具有两个记录的用户，我需要删除所有带有category_id = 1262的记录-category_id = 138 and 1262因此，在上述示例中，它必须删除以下记录：

   1    |  1262

结果，执行查询后，该表必须如下所示：

user_id | category_id
----------------------
   1    |  138
   2    |  1262
   3    |  1262

Answer 1

DELETE FROM users_categories
WHERE category_id=1262 
AND user_id IN 
    (SELECT user_id 
     FROM users_categories 
     WHERE  category_id in (138,1262)
     GROUP BY user_id 
    HAVING count(DISTINCT category_id) =2)

Answer 2

使用exists：

delete from user_categories uc
where category_id = 1262 and
      exists (select 1
              from user_categories uc2
              where uc2.user_id = u.user_id and uc2.category_id = 138
             );

从表中删除在同一表中具有另一条记录的用户的记录

2 个答案: