Use wcf-sql to call procedure

Question

when i use wcf-sql to call store procedure, i got problem:
the store procedure like this:
@variable_1 varchar(300);
@variable_2 varchar(300);
@variable_3 int;
if LEN(@variable_1)<=1
begin
     set @variable_2=0;
end
else
    set @variable_2=substring(@variable_1,1,LEN(@variable_1)-1); 
    set @variable_3= checksum(@variable_2);
when the input parameter @variable_1 is empty value, it will raise two error: 1: invalid length parameter passed to the SUBSTRING function. 2: function "checksum" request at least 1 argument(s).
 it's so strange! how can i avoid this issue?

Answer 1

Hi Jacky,
Substring function can have length as positive integer only.
SUBSTRING ( expression ,start , length )
Length is a positive integer or bigint expression that specifies how many characters of the
expression will be returned. If
length is negative, an error is generated and the statement is terminated. If the sum of
start and
length is greater than the number of characters in
expression, the whole value expression beginning at
start is returned.
Error (invalid length parameter passed to the SUBSTRING function) is result of this.
i.e. when variable_1 = 0, length will return a negative integer.
Error (function "checksum" request at least 1 argument(s)) is because the variable_2 is not assigned any value due to Error 1.
Rachit
       thanks Rachit, but if @variable_1 is empty value,it should not execute
"else" part. this is my question. how can it happen?