All, Is it expected behavior if adding "insert into xxxx" at the beginning of a sql query completely alters the output of explain? Without the "insert into", explain returns 1490 tuples, but when I add it, explain only returns 88. I was expecting that the number would go up, i.e. that the original plan would be wrapped in some additional commands which would implement the "insert into" part. Here is my sql: explain insert into aggr select 'CHANNEL', s.product, s.coupon, s.productionyear, s.tpoflag, sum(1), sum(d.scheduled)/1000000, sum(d.realized )/1000000, round(100*(1-power(sum(d.realized)/sum(d.scheduled),12)),3) as cpr from stt s, dyn d where s.loanseqnum = d.loanseqnum group by s.product, s.coupon, s.productionyear, s.tpoflag having sum(d.scheduled) > 0 ;