sql - 如何在一个 SELECT 查询中查看 2 个姓名

Question

我想从用户表中获取两个用户名，方法是将它们与我的 cases 表中的 usrID 和 res_usrID 字段进行匹配，以查看他们的姓名来自带有 usrGivenName 字段的 users 表。我想在同一行查看它们。我怎样才能做到这一点？

SELECT 
         caseID
      ,c.date_created
      ,c.date_approval_request
      ,c.date_closed
      ,u.usrGivenName 
      ,c.muh_usrID
  FROM cases AS c
  JOIN users AS u ON c.usrID=u.usrID

Answer 1

只需使用 self join (即，附加连接到同一个表):

SELECT 
        c.caseID
      , c.date_created
      , c.date_approval_request
      , c.date_closed
      , u1.usrGivenName as user_name
      , c.muh_usrID
      , u2.usrGivenName as res_user_name

FROM cases AS c
JOIN users AS u1 ON c.usrID = u.usrID
JOIN users AS u2 ON c.res_usrID = u.usrID