using if statement in sql function

Question

i have a code like this

create function factfind(@num integer) 
returns integer 
as
begin
if   (@num=1) then
return 1;
else
return(@num*factfind(@num-1));
end if;
end

errors was that, Msg 156, Level 15, State 1, Procedure factfind, Line 5 Incorrect syntax near the keyword 'then'. Msg 156, Level 15, State 1, Procedure factfind, Line 7 Incorrect syntax near the keyword 'else'. Msg 195, Level 15, State 10, Procedure factfind, Line 8 'factfind' is not a recognized built-in function name.

please help me friends.

Answer 1

...
begin
    return ( CASE
                WHEN @num=1 THEN 1
                ELSE @num * dbo.factfind(@num-1)
             END
        );
end

Edit: needs to be dbo.factfind because scalar udfs must be schema qualified

Answer 2

Execute this:

CREATE FUNCTION dbo.fakultät(@n DECIMAL(38,0))
RETURNS DECIMAL(38,0)
AS
BEGIN
DECLARE @tmp DECIMAL(38,0)
    IF (@n <= 1)
        SELECT @tmp = 1
 ELSE
  SELECT @tmp = @n * dbo.fakultät(@n - 1)
 RETURN @tmp
END

or:

CREATE FUNCTION dbo.Factorial ( @iNumber int )
RETURNS INT
AS
BEGIN
DECLARE @i  int

    IF @iNumber <= 1
        SET @i = 1
    ELSE
        SET @i = @iNumber * dbo.Factorial( @iNumber - 1 )
RETURN (@i)
END