You made the mistake of using ISNUMERIC to check for digits. ISNUMERIC does not equal ISALLDIGITS... try this and see what I mean...
Rather than just have it return a check digit, why not have it validate the ABA routing number altogether? For example...
DECLARE @RoutingNumber VARCHAR(8000) --Allows check of wrong size numbers
SET @RoutingNumber = '067803457'
AND @RoutingNumber NOT LIKE '%[^0-9]%' --Check to make sure is all digits
AND RIGHT(@RoutingNumber ,1)
= (--==== Calculates check digit (Digit 9)
SELECT 10-SUM(mv.DigitVal)%10 --Sum of individual digit values subtracted for new number ending in 0
FROM (--==== Gets multiplied value for each digit in 3, 7, 1 pattern
WHEN (t.N-1)%3 = 0 THEN SUBSTRING(@RoutingNumber,t.N,1)*3 --Digits 1,4,7
WHEN (t.N-1)%3 = 1 THEN SUBSTRING(@RoutingNumber,t.N,1)*7 --Digits 2,5,8
WHEN (t.N-1)%3 = 2 THEN SUBSTRING(@RoutingNumber,t.N,1)*1 --Digits 3,6
END AS DigitVal
FROM dbo.Tally t --See http://www.sqlservercentral.com/scripts/Advanced+SQL/62486/
WHERE t.N <= 8
ELSE 'Not Valid'
is pronounced ree-bar and is a Modenism for R
First step towards the paradigm shift of writing Set Based code: Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair
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