IF LEN(@tcSaleNo) = 0
  -- Only spaces
...

-- If string includes numbers only
IF CAST(@tcSaleNo AS int) = 0
  -- Only spaces or 0's
...

>I'm experimenting with creating a UDF to return a current customer balance. Here's the code I have so far...
>
>

>ALTER FUNCTION [dbo].[GetCustomerBalance]
>(
>	-- Add the parameters for the function here
>	@tcSaleNo Char(6)
>	)
>RETURNS Money
>AS
>BEGIN
>	-- Declare the return variable here
>	DECLARE  @yContractTotal Money
>	DECLARE  @yPaidTotal Money
>
>	-- Add the T-SQL statements to compute the return value here
>	SET @yContractTotal = (SELECT SUM(yBALANCE)
>							FROM dbo.TRANX
>							WHERE cTRANNO = @tcSaleNo
>								AND UPPER(cPMTMETHOD) = 'ACCOUNT')
>	SET @yPaidTotal = (SELECT SUM(yPAIDIN)
>							FROM dbo.TRANX
>							WHERE cCONTRACT = @tcSaleNo
>								AND lLATECHARGE <> 1)
>
>	-- Return the result of the function
>	RETURN (ISNULL(@yContractTotal, 0) - ISNULL(@yPaidTotal, 0))
>
>END
>

>
>I'm thinking I'm losing some performance and getting bad data due to the parameter being blank or zero in some cases. In VFP, I'd check for IF NOT EMPTY(tcSaleNo) and return 0. What's the best way to do the same in a SQL Server (2005) UDF?