sql - sql连接具有2个id的表

Question

我有这个表(用户和 session ):

UserId | Name
   1   | John
   2   | Linda
   3   | David

和

UserId_1 | UserId_2 | MeetingDate
   1     |     2    |  15/01/2018
   3     |     2    |  17/01/2018
   1     |     3    |  19/01/2018

如何从 2 个表中进行选择，以便在每一行中获取与每个 id 关联的名称？我想得到这样的东西:

UserId_1 | UserId_2 | User_1_Name | User_2_Name | MeetingDate
   1     |     2    |    John     |    Linda    |  15/01/2018
   3     |     2    |    David    |    Linda    |  17/01/2018
   1     |     3    |    John     |    David    |  19/01/2018

谢谢你。

Answer 1

你只需要两个内连接:

SELECT m.UserId_1
    ,m.UserId_2
    ,u1.NAME
    ,u2.NAME
    ,m.MeetingDate
FROM Meetings m
INNER JOIN Users u1 ON u1.UserId = m.UserId_1
INNER JOIN Users u2 ON u2.UserId = m.UserId_2