sql查询重复数据，删除重复数据

--查询出重复部门名称的信息1
select * from cc_mstr as a ,(select cc_desc  from cc_mstr  group by cc_desc having count(*)>1) b
where a.cc_desc =b.cc_desc
--查询出重复部门名称的信息2
select * from cc_mstr as a where (select count(*) from cc_mstr as b where a.cc_desc = b.cc_desc)>1
--查询出重复部门名称的信息3
select cc_desc
from cc_mstr
group by cc_desc
having count(*)>1

---删除cc_mstr里部门名称cc_desc   的重复记录 (保留一条)
Delete cc_mstr Where cc_code Not In (Select Max(cc_code) From cc_mstr Group By cc_desc)

1. 删除全部重复记录（慎用）
Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2. 保留一条（这个应该是你所需要的）
Delete 表 Where ID Not In (Select Max(ID) From  表 Group By 重复字段)
注：此处保留ID最大一条记录