Expression times out when running query

I am trying to get the maximum date for each record.  There are numerous records for each NDC and I need to get the NDC record which has the maximum time stamp for each different NDC how can I do this without the expression timeing out.

thanks

SELECT     r.NPT_PRICEx, r.NDC, r.NPT_DATEC
FROM         RNP2 r INNER JOIN
                          (SELECT     MAX(npt_datec) AS maxbbdc, NDC
                            FROM          rnp2
                            GROUP BY NDC) a ON r.NDC = a.NDC AND r.NPT_DATEC = a.maxbbdc
WHERE     (r.NPT_TYPE = '01')

Select allOpen in new window