Oracle删除重复数据并且只留其中一条数据

数据库操作中，经常会因为导数据造成数据重复，需要进行数据清理，去掉冗余的数据，只保留正确的数据

一：重复数据根据单个字段进行判断

1、首先，查询表中多余的数据，由关键字段（name）来查询。

select * from   table_name  where name in (select name from table_name  group by name having count(name)>1)

2、删除表中重复数据，重复数据是根据单个字段（name）来判断，只留有rowid最小的记录

delete from   table_name where (name) in 

(select Name from table_name  group by name having count(name ) >1) 

and rowid not in (select min(rowid) from OA_ADDRESS_BOOK group by Name having count(name )>1)

二：重复数据根据多个字段进行判断

1、首先，查询表中重复数据，由关键字段（name ,UNIT_ID）来查询。

select * from   table_name t1  where (t1.name,t1.unit_id) in 
(select t2.name,t2.unit_id from table_name  t2 group by  t2.name,t2.unit_id  having count(*)>1)

2、删除表中重复数据，重复数据是根据多个字段（name,UNIT_ID）来判断，只留有rowid最小的记录

delete from table_name a where (a.name,a.UNIT_ID) in 
(select name,UNIT_ID from table_name group by name,UNIT_ID having count(*) > 1) 
and rowid not in (select min(rowid) from table_name group by name,UNIT_ID having count(*)>1)

3、查询表中重复数据，重复数据是根据多个字段（name,UNIT_ID）来判断，不包含rowid最小的记录

select name,unit_id from table_name a where (a.Name,a.UNIT_ID) in 
(select Name,UNIT_ID from table_name group by name,UNIT_ID having count(*) > 1) 
and rowid not in (select min(rowid) from table_name group by Name,UNIT_ID having count(*)>1)