MSSQL查詢問題

Question

我有三個表

-Projects(ProjectId[PK], Status ...) 
-UserProjects(UserProectId[PK], ProectId[FK], UserId[FK], ...) 
-Users(UserId[PK], ...) 

我想選擇與狀態= 1，工程項目必須項目，用戶不參與。

這裏是I`ve嘗試：

Select UP.ProjectId from UserProjects UP 
Join Projects P on UP.ProjectId = P.ProjectId 
Where P.Status = 1 AND UP.UserId != 1 

結果，我想應該是公正16.這讓我也17，因爲用戶1和用戶3在項目17

任何人都知道如何解決這個問題？

Answer 1

您可以使用一個HAVING條款分組：

SELECT UP.ProjectId 
FROM UserProjects UP 
INNER JOIN Projects P ON UP.ProjectId = P.ProjectId 
WHERE P.Status = 1 
GROUP BY UP.ProjectId 
HAVING COUNT(CASE WHEN UP.UserId = 1 THEN 1 END) = 0 

的HAVING子句過濾掉與用戶與UserId = 1項目。

或者您可以使用NOT EXISTS：

SELECT ProjectId 
FROM Projects AS P 
WHERE Status = 1 AND 
     NOT EXISTS(SELECT 1 
       FROM UserProjects AS UP 
       WHERE UP.ProjectId = P.ProjectId AND UP.UserId = 1)