mysql - 实现 Mysql 连接。如何获得同一行的结果？

Question

Er 图链接:

我想从子表中获取数据。例如。我需要所有 user_id 的位置、设备、语言、服务。对于给定的 user_id，位置、设备、语言和服务有多个值。

我尝试了以下代码:

SELECT  user_detail.user_id , user_detail.name , user_equipment.equipment , user_location.location , user_service.service , user_language.language
          from user_detail
    INNER JOIN user_equipment on user_detail.user_id = user_equipment.user_id
    INNER JOIN  user_location on user_detail.user_id = user_location.user_id
    INNER JOIN user_service on user_detail.user_id = user_service.user_id
    INNER JOIN user_language on user_detail.user_id = user_language.user_id;

现在的问题是，如果 user_id 有三个位置，我得到三行，有什么方法可以让所有位置都在同一行中？

Answer 1

您正在寻找此“GROUP_CONCAT”，您的查询将如下所示:

SELECT  user_detail.user_id ,
    user_detail.name,
    GROUP_CONCAT(user_equipment.equipment SEPARATOR ',') as equipments,
    GROUP_CONCAT(user_location.location SEPARATOR  ',') as locations,
    GROUP_CONCAT(user_service.service SEPARATOR ',') as services,     
    GROUP_CONCAT(user_language.language SEPARATOR ',') as languages
FROM user_detail
    INNER JOIN user_equipment on user_detail.user_id = user_equipment.user_id
    INNER JOIN  user_location on user_detail.user_id = user_location.user_id
    INNER JOIN user_service on user_detail.user_id = user_service.user_id
    INNER JOIN user_language on user_detail.user_id = user_language.user_id;
GROUP BY user_detail.user_id