Question

I have a query with the below WHERE clauses

WHERE
    I.new_outstandingamount = 70
    AND ISNUMERIC(SUBSTRING(RA.new_stampernumber,7, 4)) = 1
    AND (DATEDIFF(M,T.new_commencementdate, SUBSTRING(RA.new_stampernumber,7, 10)) >= 1)
    AND RA.new_applicationstatusname = 'Complete'
    AND I.new_feereceived > 0
    AND RA.new_stampernumber IS NOT NULL
    AND T.new_commencementdate IS NOT NULL

RA.new_stampernumber is a string value which contains three concatenated pieces of information of uniform length. The middle piece of info in this string is a date in the format yyyy-MM-dd.

In order to filter out any rows where the date in this string in not formatted as expected I do a check to see if the first 4 characters are numeric using the ISNUMERIC function.

When I run the query I get an error message saying

The conversion of a nvarchar data type to a datetime data type resulted in an out-of-range value.

The line that is causing this error to occur is

AND (DATEDIFF(M,T.new_commencementdate, SUBSTRING(RA.new_stampernumber,7, 10)) >= 1)

When I comment out this line I don’t get an error.

What is strange is that if I replace

AND ISNUMERIC(SUBSTRING(RA.new_stampernumber,7, 4)) = 1

with

AND SUBSTRING(RA.new_stampernumber,7, 4) IN ('2003','2004','2005','2006','2007','2008','2009','2010', '2011', '2012','2013','2014','2015'))

the query runs successfully.

Whats even more strange is that if I replace the above working line with this

AND SUBSTRING(RA.new_stampernumber,11, 1) = '-'

I get the error message again. But if I replace the equals sign with a LIKE comparison it works:

AND SUBSTRING(RA.new_stampernumber,11, 1) LIKE '-'

When I remove the DATEDIFF function and compare the results of each of these queries they all return the same resultset so it is not being caused by different data being returned by the different clauses.

Can anyone explain to me what could be causing the out-of-range error to be thrown for some clauses and not for others if the data being returned is in fact the same for each clause?

Thanks,
Neil

Answer 1

Different execution plans.

There is no guarantee that the WHERE clauses are processed in particular order. Presumably when it works it happens to filter out erroring rows before attempting the cast to date.

Also ISNUMERIC itself isn’t very reliable for what you want. I’d change the DATEDIFF expression to something like the below

DATEDIFF(M, T.new_commencementdate, 
                    CASE
                    WHEN RA.new_stampernumber LIKE 
                    '______[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]%' 
                     THEN SUBSTRING(RA.new_stampernumber, 7, 10)
                     END) >= 1 )