來自 王濤 同志的指導
DELETE FROM product WHERE searchdate IN (SELECT sd FROM (SELECT a.searchdate sd FROM product a GROUP BY a.searchdate HAVING count(a.searchdate) > 1 ) t)AND iid NOT IN (SELECT mid FROM(SELECT min(b.iid) mid FROM product b GROUP BY b.searchdate HAVING count(b.searchdate) > 1) st
);