Paging in Gridview

I have a Data set which in which i am getting data twice from tow different tables one is clients and another is organization table and in the select statement i have made the no and names of the column similar now i have binded a grid view with this data set all is fine till here the now i apply paging to this grid the paging is working fine till the page contains data from the first table but it displays the last page of the first table if the page index related too second tables are clicked any help will be highly appreciated