Question

第三个选择节目显示前两个选择的重复结果。所以我说我的数据集只有5个ID。前两个语句生成id 1,2,3 enabled = 1 我需要的最后一个语句ids4,5 enabled = 0

但是现在我得到id 1,2,3,4,5启用= 1 PLUS ID 1,2,3,4,5 enabled = 0

SELECT p.*, 1 as enabled
    FROM member_permissions mp
    JOIN permissions p ON p.permission_id = mp.permission_id
    WHERE member_id = 1
UNION
    SELECT pgp.*, 1 as enabled
    FROM member_permissions mp
    JOIN permission_link pl ON pl.permission_group_id = mp.permission_group_id
    JOIN permissions pgp ON pgp.permission_id = pl.permission_id
    WHERE member_id = 1
UNION
    SELECT *, 0 as enabled
    FROM permissions p

Answer 1

不幸的是，您必须执行两次顶级查询才能从较低的查询中删除它们：

FriendsOfCake/cakephp-csvview

Answer 2

在这种情况下，您可以尝试使用左连接。

SELECT DISTINCT
       prm.*,
       CASE
         WHEN mp.member_id IS NULL OR mp2.member_id IS NULL THEN 0
         ELSE 1
       END AS ENABLED
  FROM permissions prm
  LEFT JOIN member_permissions mp
         ON mp.permission_id = prm.permission_id
        AND mp.member_id = 1
  LEFT JOIN permission_link pl
         ON pl.permission_group_id = prm.permission_group_id
  LEFT JOIN member_permissions mp2
         ON mp2.permission_group_id = pl.permission_group_id
        AND mp2.member_id = 1

不是我认为的最佳解决方案，但可能有效

mysql：不要在SELECT上显示重复的结果

2 个答案: