Select DISTINCT(yr) from (select year(issue_date) as yr, issue_date from paper_master,np_master,stamps where issue_date!='' and  paper_master.paper_code=stamps.paper_code and paper_master.paper='Unwatermarked Gummed coated stamp paper'  and np_master.np_code=stamps.np_code and np_master.np='P'  order by issue_date) t