Create Function Must Be the Only Statement in the Batch

The function needs to be either the only function in the query window OR the only statement in the batch. If there are more statements in the query window, you can make it the only one "in the batch" by surrounding it with GO's.

e.g.

GO
CREATE FUNCTION getLavel(@id int ,@lavel char)
RETURNS date
BEGIN
 DECLARE @date date
    select @date = (select authorization_date from Authorized WHERE     diver_number = @id and @lavel =level_name)
    return @date
END
GO

You need to add RETURN before the END statement

That should fix your issue, that's what fixed mine. :D

Make sure that this statement is the only the only sql in your query window before you execute it.

Or you can highlight the function declaration and execute

What solved it for me, was that I was trying to create the function inside of a transaction context - that doesn't make sense from a SQL Server point of view. Transactions are for data, not functions.

Take the CREATE FUNCTION statement out of the transaction, then wrap it in GO's

CREATE FUNCTION CalculateAge(@DOB  DATE) 
RETURNS INT 
AS
BEGIN
DECLARE @Age INT
SET @DOB='08/12/1990'
SET @Age =DATEDIFF(YEAR,@DOB,GETDATE()) -
   CASE
        WHEN (MONTH (@DOB)>  MONTH (GETDATE ())) OR
             (MONTH (@DOB)= MONTH (GETDATE ())  AND DAY (@DOB) >DAY (GETDATE ()))

    THEN 1 
    ELSE 0
    END 
SELECT @Age
END

The Error is given to you in only query Page But if you execute the query then it will successfully execute.

CREATE FUNCTION getLavel(@id int ,@lavel char)
RETURNS date
BEGIN
 DECLARE @date date
    select @date = (select authorization_date from Authorized WHERE diver_number = @id and @lavel = level_name)
    return @date
END
GO