oracle基本语句

去掉重复记录

select * from company where comid in (select Max(comid) from company

group by companyname)

得到重复记录数

select * from company where comid not in (select Max(comid) from company

group by companyname)

对完全相同的记录可以使用 DISTINCT 对记录进行唯一性过滤