Question

我需要一些代码的帮助

我有一个名为“stuff”的数据库表，我有这个信息：

+------+-------------+---------------------+
| id   | member_id   |     group_id        |
+------+-------------+---------------------+
| 1    |      11     |         aa          |
+------+-------------+---------------------+
| 2    |      11     |         bb          |
+------+-------------+---------------------+
| 3    |      22     |         bb          |
+------+-------------+---------------------+
| 4    |      11     |         cc          |
+------+-------------+---------------------+
| 5    |      22     |         cc          |
+------+-------------+---------------------+
| 6    |      33     |         cc          |
+------+-------------+---------------------+

我需要的是什么：

If I search for group_id when member_id = 11 the result will be aa
If I search for group_id when member_id = 11 AND member_id = 22 the result will be bb
If I search for group_id when member_id = 11 AND member_id = 22 AND member_id = 33 the result will be cc

Answer 1

您可以在select语句中使用IN()运算符：

SELECT * FROM stuff
WHERE member_id IN(11,22,33);

在您的前端，您可以连接值或用逗号分隔的member_id。

Answer 2

SELECT  group_id
FROM    stuff
GROUP   BY group_id
HAVING  SUM(member_id = 11) = 1
        AND SUM(member_id = 22) = 1
        AND COUNT(*) = 2

SQLFiddle Demo

另一种变体，

SELECT  group_id
FROM    stuff a
WHERE   member_id IN (11,22,33)                 -- <<== list of member_id
        AND
        EXISTS
        (
          SELECT group_id
          FROM stuff b
          WHERE a.group_id = b.group_id
          GROUP BY group_id
          HAVING COUNT(*) = 3                   -- <<== number of member_id
        )
GROUP   BY group_id
HAVING  COUNT(*) = 3                            -- <<== number of member_id

SQLFiddle Demo

Answer 3

请注意，member_id不能同时是11和22.你是说OR吗？以下2个查询将始终返回null：

search for group_id when member_id = 11 AND member_id = 22
search for group_id when member_id = 11 AND member_id = 22 AND member_id = 33

SQL获取组ID的唯一值，其中成员标识为一个或多个

3 个答案: