Oracle 去重

Oracle 删除重复数据只留一条

查询及删除重复记录的SQL语句
 
-- 1、查找表中多余的重复记录，重复记录是根据单个字段（Id）来判断
select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)
 
-- 例:
select * from orders_tmp2 where cust_nbr in
(select cust_nbr from orders_tmp2 group by cust_nbr having count(cust_nbr) > 1)
 
-- 2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有 rowid 最小的记录
DELETE from 表 WHERE (id) IN 
    ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) 
    AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);
 
-- 3、查找表中多余的重复记录（多个字段）
select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,seq having count(*) > 1)
 
-- 4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
delete from 表 a where (a.Id,a.seq) in 
    (select Id,seq from 表 group by Id,seq having count(*) > 1) 
    and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)
 
-- 5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
 select * from 表 a where (a.Id,a.seq) in 
    (select Id,seq from 表 group by Id,seq having count(*) > 1) 
    and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)
    
-- 去重, cust_nbr,month 为主键, cust_nbr 相同,只留下month最大的记录
delete from orders_tmp2 where (cust_nbr, month) not in 
(select cust_nbr,
max(month) keep(dense_rank first order by month desc) max_month
from orders_tmp2 tb group by cust_nbr)