函数返回null

Question

ALTER FUNCTION [dbo].[getCourseCost] 
(
    @CourseCode varchar(50), 
    @Year nchar(10), 
    @Period nchar(10) 
) 
RETURNS int 
AS 
BEGIN 
DECLARE @Pnr_personal varchar(50) 
DECLARE @Timlön_personal int 
DECLARE @Antal_timmar_personal int 
DECLARE @Kostnad_personal int 
DECLARE @Kostnad_labass int 

SELECT @Pnr_personal = Personnummer FROM Bemannas_Av WHERE Period = @Period AND Läsår =     @Year AND Kurskod = @CourseCode 
SELECT @Timlön_personal = Timlön FROM Personal WHERE Personnummer = @Pnr_personal 
SELECT @Antal_timmar_personal = Antal_Timmar FROM Bemannas_Av WHERE Period = @Period AND Läsår = @Year AND Kurskod = @CourseCode 
SELECT @Kostnad_labass = (Antal_timmar * Timlön) FROM Labass WHERE Period = @Period AND Läsår = @Year AND Kurser = @CourseCode 

SET @Kostnad_personal = @Timlön_personal * @Antal_timmar_personal 
IF @Kostnad_personal = NULL 
BEGIN 
SET @Kostnad_personal = 0 
END 

IF @Kostnad_labass = NULL 
BEGIN 
SET @Kostnad_labass = 0 
END 

RETURN @Kostnad_personal + @Kostnad_labass 
END 

即使没有使用的值在数据库中为NULL，它仍会返回NULL。

Answer 1

该零件有问题@Kostnad_personal=null意味着什么。

IF @Kostnad_personal is NULL 
BEGIN 
SET @Kostnad_personal = 0 
END 

IF @Kostnad_labass is NULL 
BEGIN 
SET @Kostnad_labass = 0 
END 

或者使用：

RETURN ISNULL(@Kostnad_personal,0) + ISNULL(@Kostnad_labass,0)