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)

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