Hi, people

I have a table named nf with a field dataemissao( date) and a field nfnum and indexed by these fields, and a table named nfitens with foreign Key nfnum from nf table, and two fields vcofins and vpis( numeric values). I need the sum of these fields in a period of time. It's not surprise that the performance of the query that sums these( vPIS and vCOFINS) decrease with the period of time increase.
I can put the sum of vpis and vcofins for every nfnum in the nf table and the problem is solved. But is there any other idea to speed the query?

 SELECT 
 	SUM( Nfitens.vCOFINS) as VCOFINS,
 	SUM( Nfitens.vPIS) as VPIS
 	FROM 
     nf Nf inner join Nfitens on nf.nfnum=nfitens.nfnum
	 WHERE nf.dataemissao  BETWEEN  ?tddatefrom and ?tddateto