如何为特定团队每次返回唯一消息

Question

我有一个像this这样的表，其中包含团队ID和消息ID。每次运行查询时，我都必须为每个团队获得唯一 msg_id。

示例：

ID  TEAM_ID  MSG_ID
1    1        10
2    1        11
3    2        12
4    2        13
5    2        14

有效输出：

1

TEAM_ID        MSG_ID
   1             11
   2             13

2

TEAM_ID        MSG_ID
   1             10
   2             12

Answer 1

如果您想为每个TEAM_ID返回一个随机相关的MSG_ID：

SELECT t.TEAM_ID,
    (SELECT MSG_ID
     FROM team_message
     WHERE TEAM_ID = t.TEAM_ID
     ORDER BY RAND()
     LIMIT 1) MSG_ID
FROM (SELECT DISTINCT TEAM_ID
      FROM team_message) t;

SQL Fiddle

Answer 2

SELECT * FROM (SELECT * FROM team_message ORDER BY rand()) as t GROUP BY TEAM_ID;