Mysql数据库查询重复数据

Mysql数据库查询重复数据

    SELECT * from tab1 where CompanyName in( SELECT companyname from tab1 GROUP BY CompanyName HAVING COUNT(*)>1);-- 129.433ms       

    SELECT * from tab1 INNER join  ( SELECT companyname from tab1 GROUP BY CompanyName HAVING COUNT(*)>1) as tab2 USING(CompanyName);-- 0.482ms