I see alot of examples of a correlated subquery on the right of a "WHERE" clause, but what about when it is part of the select list, as follows:
select distinct t.personnum,
                t.applydate,
                round(t.wfctimeinseconds/3600,2) as amount,
                substr(c.customdata,1,1) as shift,
               (select count(*) from vp_alltotals
                    where personnum = t.personnum
                    and applydate = t.applydate
                    and wfctimeinseconds = t.wfctimeinseconds
                    and paycodename = 'Shift Differential') as NumShiftDiff
from vp_alltotals t,
vp_personcustdata c
where
c.personnum = t.personnum;

This query is really bogging down badly when this select list includes what looks to me like a correlated subquery. Are there better ways to code this ? Use temp tables ?
Gil

I don't know of any problems with using a subquery as part of the select. What is the actual problem you are having?