Why I cannot get a result value from T-SQL function

Question

I'm trying to learn function in SQL Server, and I don't know why I cannot get a proper result from a T-SQL function.

The query what creates function is:

CREATE FUNCTION yuri_func1 
     (@valDate VARCHAR(10))
RETURNS VARCHAR
AS
BEGIN
    DECLARE @valWeekday VARCHAR(10);

    SET @valWeekday = DATENAME(WEEKDAY, @valDate);

    RETURN @valWeekday;
END

And the other query is

select dbo.yuri_func1('2017-12-29') as [요일]

but the only result I got is just

Blank. (="")

But when I executed function like this,

select DATENAME(WEEKDAY, '2017-12-29')

the result was

MONDAY

I still don't get that why they return different results.

Does anybody know why?

you have not defined the size of return type correct and define the size as RETURNS VARCHAR(10) — Yogesh Sharma
– Yogesh Sharma, Commented Dec 29, 2017 at 5:17

AllanC · Accepted Answer · 2017-12-29 05:23:50Z

3

This is because you should be accepting DateTime as a parameter in your function and not varchar

create Function yuri_func1 (@valDate DateTime) --Wrong parameter type
RETURN VARCHAR(10) -- No proper sizing of return type
AS
BEGIN
    declare @valWeekday varCHAR(10);

    Set @valWeekday = DATENAME(WEEKDAY,@valDate);


    return @valWeekday;
END
GO

edited Dec 29, 2017 at 5:23

answered Dec 29, 2017 at 5:15

AllanC

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1 Comment

Yuri Over a year ago

Thanks Alander. As you commented, I changed function query. and it worked! I appreciate that ;)

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