獲取第一個表的屬性在LEFT JOIN查詢

Question

考慮表：

工人

和WorkersBosses（多對多）

我怎樣才能得到所有僱員與他們的老闆（如果一個工人有一個老闆，所以把它放在他身邊，否則就是放一個空）。

有了這個：

SELECT TOP 1000 [EmployeeName] ,workboss.bossid 
    FROM [TestingDB].[dbo].[Worker] as workers 
    LEFT OUTER JOIN [TestingDB].[dbo].[WorkersBosses] as workboss 
    on workers.EmployeeId = workboss.WorkerId 

我得到的所有與他們的老闆的員工，但我怎麼能得到也是老闆的名字（不只是他的ID）？

感謝

Answer 1

添加INNER JOIN到Worker：

SELECT 
    w.EmployeeName AS EmployeeName, 
    wb.BossName 
FROM Worker w 
LEFT JOIN(
    SELECT b.WorkerId, b.BossId, w2.EmployeeName AS BossName 
    FROM WorkersBoss b 
    INNER JOIN Worker w2 
     ON w2.EmployeeId = b.BossId 
)wb 
    ON w.EmployeeId = wb.WorkerId 

這也可以寫成：

SELECT 
    w.EmployeeName AS EmployeeName, 
    w2.EmployeeName AS BossName 
FROM Worker w 
LEFT JOIN WorkersBosses wb 
    INNER JOIN Worker w2 
     ON w2.EmployeeId = wb.BossId 
    ON w.EmployeeId = wb.WorkerId 

Answer 2

您只需通過使用不同的別名多次加入相同的表：

SELECT w.EmployeeId, 
    w.EmployeeName, 
    b.EmployeeId AS BossEmployeeId, 
    b.EmployeeName AS BossEmployeeName 
FROM Worker w 
LEFT JOIN WorkersBosses wb 
    ON wb.WorkerId = w.EmployeeId 
LEFT JOIN Worker b 
    ON b.EmployeeId = wb.BossId