sql - SQL 查询 - 同一字段上的多个联接

Question

我需要帮助构建此查询，我需要从同一个表中选择不同的值但不同的唯一键。

为了详细说明，请提供以下示例：

我有 2 张桌子：

问题（IssueID、AuthorID_FK、AssigedID_FK、...）
用户（UserID、User_Label、...）

AuthorID_FK和AssigedID_FK都链接到表用户，我需要在相同的查询结果中获取两者的User_Label。

你能帮忙吗？

谢谢，

Answer 1

SELECT a.IssueID, b.User_Label, c.User_Label FROM Issues a
INNER JOIN USERS b on a.AuthorID_FK = b.UserID
INNER JOIN USERS c on a.AssignedID_FK = c.UserID

类似的东西 :) 这应该在 MS SQL Server 中工作

Answer 2

好吧，这个也应该工作:)

SELECT IssueID, U.User_Label FROM Issues I
INNER JOIN Users U ON U.UserID = I.AuthorID_FK

UNION

SELECT IssueID, U.User_Label FROM Issues I
INNER JOIN Users U ON U.UserID = I.AssigedID_FK

Answer 3

惯于

SELECT a.IssueID, b.UserID 
FROM Issues a 
    JOIN Users b ON (a.AuthorID_FK=b.UserID OR a.AssignedID_FK = b.UserID)

工作？

Answer 4

您可能想尝试这样的事情

SELECT
    issues.IssueID,
    Authour.User_Label AS Author_Label,
    Assigned.User_Label AS Assigned_user_Label
FROM
    issues
    INNER JOIN users AS Authour ON Authour.UserID = issues.AuthorID_FK
    INNER JOIN users AS Assigned ON Assigned.UserID = issues.AssignedID_FK