为什么我的存储过程返回0？

Question

我想获得pointsEarned列的总和和pointsPossible列的总和。我想把它变成一个百分比。我的问题是，我的SP总是返回0，即使在有给定enrollmentId的行具有先前列的值时也是如此。

我在做什么错？

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 

这是数据库表：

我执行存储过程和在69的enrollmentId传递，它仍然返回0

Answer 1

整数用分母除法（pointsPossible ）大于分子（pointsEarned）返回零。

写为（修订）：

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，因为这个过程会返回一个标值，它可能更适合将它定义为一个函数，而不是一个存储过程。

Answer 2

1. 使用简单SUM没有OVER。

2. RETURN只能返回int。如果您的百分比低于100％，则整数除法将始终返回0，因此乘以100将返回整个百分比而不是比率。

3. 检查你没有被零除。

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