you mean i should post my struture?.......

i don't know my statement what problem ............. how can i do?

select distinct (c.candidate_no)  FROM ((candidate as c left JOIN education as e ON  c.candidate_no = e.candidate_no ) left Join working as w ON c.candidate_no = w.candidate_no )group by c.candidate_no having  sum(datediff('yyyy','01/01/' & w.from_year ,'01/01/' & w.to_year )) >= 1