쿼리문 where에 sum을 사용하지 못하나요?

select a.mb_id, b.mb_name, sum(a.wr_23) as tot
      from {$write_table} a
               left outer join {$g5['member_table']} b on a.mb_id = b.mb_id
     where a.wr_29 between '{$stx1}' and '{$stx2}' and sum(a.wr_23) < 1540000
     group by a.mb_id, b.mb_name
     ORDER BY tot DESC

select a.mb_id, b.mb_name, sum(a.wr_23) as tot
      from {$write_table} a
               left outer join {$g5['member_table']} b on a.mb_id = b.mb_id
     where a.wr_29 between '{$stx1}' and '{$stx2}' and tot < 1540000
     group by a.mb_id, b.mb_name
     ORDER BY tot DESC