如何在SQL查詢中使用的情況下

Question

我的查詢低於

SELECT *, 
CASE WHEN SUBSTRING(controlId,1,1) = 'M' THEN (select fullname from master as controler 
where Regular.controlId = Master.MasterId) 

WHEN SUBSTRING(controlId,1,1) = 'A' THEN (select fullname from Admin as controler 
where Regular.controlId = Master.AdminId) 
END AS controler 
FROM Regular 
INNER JOIN Master ON Regular.ControlId = Master.MasterId 
INNER JOIN Admin ON Regular.ControlId = Admin.AdminId 
Where (Regular.active=0) 

我的表

我的正常數據

我的主表

我的聯繫表中的數據

我想從每一行相關型號表中的全名，但使用上面的代碼它沒有給出任何結果....

Answer 1

這個數據似乎標準化很差，而且也沒有在這個問題足夠的信息知道發生了什麼，但我懷疑你的連接是錯誤的，而且你確實需要使用LEFT連接而不是INNER連接。然後，您可以使用COALESCE（）函數代替CASE子句：

SELECT r.*, COALESCE(m.FullName, a.FullName, r.FullName) FullName 
FROM Regular r 
LEFT JOIN Master m ON r.ControlId = m.MasterId 
LEFT JOIN Admin a ON r.ControlId = a.AdminId 
WHERE r.active=0 

Answer 2

我不能使用INNER JOIN小號

INNER JOIN Master ON Regular.ControlId = Master.MasterId 
INNER JOIN Admin ON Regular.ControlId = Admin.AdminId 

Regular.ControlId不能存在兩個表中列Master和Admin

SELECT *, 
CASE WHEN SUBSTRING(controlId,1,1) = 'M' THEN (select fullname from master as controler 
where Regular.controlId = Master.MasterId) 

WHEN SUBSTRING(controlId,1,1) = 'A' THEN (select fullname from Admin as controler 
where Regular.controlId = Master.AdminId) 
END AS controler 
FROM Regular 
Where (Regular.active=0) 

Answer 3

也許因爲內部聯接。嘗試改變：

SELECT *, 
    CASE WHEN SUBSTRING(controlId,1,1) = 'M' THEN (select top 1 fullname from Master 
    where Regular.controlId = Master.MasterId) 

    WHEN SUBSTRING(controlId,1,1) = 'A' THEN (select top 1 fullname from Admin 
    where Regular.controlId = Admin.AdminId) 
    END AS controler 
    FROM Regular 
    Where (Regular.active=0)