Mysql左聯接：顯示基於聯接表中另一個屬性的行

Question

我有以下表格：

   Pools                         Members                             User
----------------------------------------------------------------------------------
id      name              id     pool_id     user_id              id      name
----------------------------------------------------------------------------------
1       abc               1         1          101                101     test1
2       xyz               2         1          102                102     test2
                          3         2          105                105     test5
                          4         2          106                106     test6

當用戶登錄時，他應查看其不屬於其成員的那些池的列表，例如，如果登錄ID為101的用戶，則應顯示以下結果。

Pool              Members
xyz                2 members

Answer 1

可能是您想要的

SELECT name AS Pool,
       count(pool_id) AS Members
FROM Pools
JOIN Members ON Pools.id=Members.pool_id
WHERE Pool.id NOT IN
    (SELECT pool_id
     FROM Members
     WHERE user_id=101)
GROUP BY Member.pool_id