mysql - 同一张表上的多个联接

Question

我正在尝试实现一个看似简单的查询，但我无法使其正常工作。这是我的数据库表结构:

members
    -> id
    -> last_name
    -> first_name

activities
    -> id

registrations
    -> id
    -> member_id

tandems
    -> id
    -> activitie_id
    -> registration_member_one
    -> registration_member_two

这就是我想要实现的目标:

多个成员(member)可以注册参加一项事件。然后，我将注册按串联进行分组。我想要一个列出所有串联的 View ，这就是我的问题。当我尝试查询时，它给出了多行，重复了很多次。

下面是我想要的表格示例:

tandems.id | activities.id | registration_member_one.members.last_name | registration_member_two.members.last_name
1          | 3             | John Doe                                  | Jane Doe

这是我正在处理的查询:

SELECT
tandems.*,
memberOne.id, memberOne.last_name, memberOne.first_name,
memberTwo.id, memberTwo.last_name, memberTwo.first_name,
memberOne_registration.member_id as memberOne,
memberTwo_registration.member_id as memberTwo

FROM tandems

JOIN registrations as memberOne_registration
ON memberOne_registration.member_id = tandems.registration_member_one
JOIN members as memberOne ON memberOne.id = memberOne_registration.member_id

JOIN registrations as memberTwo_registration
ON memberTwo_registration.member_id = tandems.registration_member_two
JOIN members as memberTwo ON memberTwo.id = memberTwo_registration.member_id

WHERE activitie_id = 3;

感谢任何帮助!

Answer 1

该错误是由于将 registrations 表的错误列 (member_id) 与 tandems 表连接所致，而不是列 registrations.id应该使用。

SELECT
tandems.*,
memberOne.id, memberOne.last_name, memberOne.first_name,
memberTwo.id, memberTwo.last_name, memberTwo.first_name,
memberOne_registration.id as memberOne,
memberTwo_registration.id as memberTwo

FROM tandems
JOIN registrations as memberOne_registration ON memberOne_registration.id = tandems.registration_member_one
JOIN members as memberOne ON memberOne.id = memberOne_registration.member_id
JOIN registrations as memberTwo_registration ON memberTwo_registration.id = tandems.registration_member_two
JOIN members as memberTwo ON memberTwo.id = memberTwo_registration.member_id

WHERE activitie_id = 3;