爲什麼我的存儲過程返回0？

Question

我想獲得pointsEarned列的總和和pointsPossible列的總和。我想把它變成一個百分比。我的問題是，我的SP總是返回0，即使在有給定enrollmentId的行具有先前列的值時也是如此。

我在做什麼錯？

ALTER PROCEDURE GetPercentage 
    @enrollmentId int 
AS 
BEGIN 
    DECLARE @pointsEarned int; 
    DECLARE @pointsPossible int; 

    SET NOCOUNT ON; 

    SELECT 
     @pointsEarned = CAST(SUM(pointsEarned) OVER() AS decimal), 
     @pointsPossible = CAST(SUM(pointsPossible) OVER() AS decimal) 
    FROM 
     Assignments 
    WHERE 
     enrollmentId = @enrollmentId 

    RETURN @pointsEarned/@pointsPossible 
END 
GO 

這是數據庫表：

我執行存儲過程和在69的enrollmentId傳遞，它仍然返回0

Answer 1

整數用分母除法（pointsPossible ）大於分子（pointsEarned）返回零。

寫爲（修訂）：

ALTER PROCEDURE GetPercentage 
    @enrollmentId int 
AS 
BEGIN 
    SET NOCOUNT ON; 

    SELECT 
     Percent = case when sum(pointsPossible) > 0 then (1.0 * sum(pointsEarned))/sum(pointsPossible) else 0 end 
    FROM 
     Assignments 
    WHERE 
     enrollmentId = @enrollmentId 
    GROUP BY 
     enrollmentId 
END 
GO 

正如@ Nick.McDermaid指出，因爲這個過程會返回一個標值，它可能更適合將它定義爲一個函數，而不是一個存儲過程。

Answer 2

1. 使用簡單SUM沒有OVER。

2. RETURN只能返回int。如果您的百分比低於100％，則整數除法將始終返回0，因此乘以100將返回整個百分比而不是比率。

3. 檢查你沒有被零除。

程序

ALTER PROCEDURE GetPercentage 
    @enrollmentId int 
AS 
BEGIN 
    SET NOCOUNT ON; 

    DECLARE @pointsEarned int; 
    DECLARE @pointsPossible int; 

    SELECT 
     @pointsEarned = SUM(pointsEarned), 
     @pointsPossible = SUM(pointsPossible) 
    FROM 
     Assignments 
    WHERE 
     enrollmentId = @enrollmentId 
    ; 

    RETURN 
     CASE WHEN @pointsPossible <> 0 
     THEN 100 * @pointsEarned/@pointsPossible 
     ELSE 0 END; 

END 
GO