dongnaoben4456 2015-06-16 15:43
浏览 28
已采纳

Mysql Many to Many with Mapping表返回一行并连接会导致重复行的值

I am using mysql and have three tables one for events one for officials and a mapping table between. How would I query so that the following takes place:

  • One single row per event
  • Concatenate the multiple values for officials into the corresponding single event row.

Tables are structures as such:

**Official** 
-------------
id    name
-------------
1     ali
2     ahmed
3     john
4     king
6     kyle

**Event**
-------------
id    name
-------------
1     event 1
2     event 2
3     event 3

**Mapping**
-------------
id   oid   eid
-------------
1     1     1
2     3     1
3     6     2
4     1     3
5     4     3
6     5     3
7     6     3
  • 写回答

1条回答 默认 最新

  • doubang9906 2015-06-16 17:35
    关注

    You can make use of INNER JOIN and GROUP_CONCAT, see example below:-

    SELECT 
    E.id, E.name, GROUP_CONCAT(O.name) OfficialName
    FROM Mapping M 
    INNER JOIN Event E
        ON M.eid = E.id
    INNER JOIN Official O
        ON M.oid = O.id
    GROUP BY E.id
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

报告相同问题?

悬赏问题

  • ¥15 arduino控制ps2手柄一直报错
  • ¥15 使用rabbitMQ 消息队列作为url源进行多线程爬取时,总有几个url没有处理的问题。
  • ¥85 maple软件,solve求反函数,出现rootof怎么办?
  • ¥15 求chat4.0解答一道线性规划题,用lingo编程运行,第一问要求写出数学模型和lingo语言编程模型,第二问第三问解答就行,我的ddl要到了谁来求了
  • ¥15 Ubuntu在安装序列比对软件STAR时出现报错如何解决
  • ¥50 树莓派安卓APK系统签名
  • ¥65 汇编语言除法溢出问题
  • ¥15 Visual Studio问题
  • ¥20 求一个html代码,有偿
  • ¥100 关于使用MATLAB中copularnd函数的问题