I am having a problem with the following query. Why am I not able to use a
conversion function in the compute by clause.
The query runs fine without.

SELECT Datepart(month,W.ExpirationDate) , count(*)
FROM Warranty W (NOLOCK)
JOIN WarrantyRenewal WR (NOLOCK) on (w.warrantykey = wr.warrantykey)
JOIN ValueSet V (NOLOCK) on (v.valuesetkey = w.statusvskey)
WHERE W.ExpirationDate BETWEEN 'JUL 01 2000' AND 'SEP 30 2000' and
(wr.createdby = 'Resale_Load' or wr.createdby = 'New_Home_Load&#39 GROUP BY
Datepart(month,W.ExpirationDate), v.value,
convert(int,PhoneNumberExistsFlag,1),timezone
ORDER BY Datepart(month,W.ExpirationDate)
COMPUTE sum(Count(*)) BY Datepart(month,W.ExpirationDate)