Question

I’m trying to figure out how to handle an error that gets thrown at the final set statement, wherein I call substring on the current @return value and set the result the same return value.

The stored procedure takes in a string of numbers like this: ‘135, 34, 21,’. The trailing comma is an artifact of a poorly designed system. This procedure runs the string through a split function to create a temp table, and then does a look up on each of the items in the string, returning a name associated with each of the three values. The error is thrown when all three values of the parameter are 0: ‘0,0,0,’

I’m just crap with SQL Server and have no idea how to gracefully handle those situations. Could someone provide some advice for me?

Here is my stored procedure:

declare @positions table
    (orderID int identity(1,1), positionID int)
declare @counter int
declare @positionMax int
declare @currentPositionID int
declare @return varchar(max)

set @counter = 1
set @return = ''

insert @positions
select items
from dbo.Split(
    (select Positions
     from dbo.athletes
     where athleteID = 3701, ',')

select @positionMax = max(orderID) 
from @positions

while(@counter <= @positionMax)
begin
    select @currentPositionID = tp.PositionID
    from db.positions tp
        inner join @positions p
            on tp.PositionID = p.positionID
    where p.orderID = @counter

    select @return = @return + PositionName + ', '
    from dbo.positions
    where PositionID = @currentPositionID

    set @counter = @counter + 1
end

set @return = substring(@return, 1, (len(@return) - 1))

select @return

Edit with sample data and expected results

Here’s what the positions table looks like:

PositionId, PositionName
1, Defensive End
2, Quarterback
3, Pitcher
4, Catcher
5, First Base

The positions are saved in a single table row like this:

1,2,3,
1,0,0,
0,0,0,

The output would look like this:

Defensive End, Quarterback, Pitcher
Defensive End
No position selected

“No position selected” is what I’d like to have output in the instance of three zeros.

Answer 1

I’m guessing your error is caused because @return is 0 characters long. A simple option could be to add the value 0, ‘No position selected’ to the positions table.

A nicer option could be to add an IF statement around the set statement:

if len(@return) > 0
BEGIN
    set @return = substring(@return, 1, (len(@return) - 1))
END
ELSE
BEGIN
    set @return = 'No position selected'
END

You could also add a Try/Catch block if using SQL to catch any generic exceptions. See msdn try/catch

Also, not sure why you’re doing the while loop. There are generally better options in SQL like using a CTE.