Oracle 查询/删除重复记录

假设订单表tbl_order存在重复的记录：



一.查找表中存在重复的记录

1.单个字段存在重复的情况

select * from tbl_order t where t.order_no in (select t.order_no from tbl_order t group by t.order_no having count(*) > 1)

结果：

1 001
订单1

2 002 订单2

3 002 订单2

4 001 订单1

2.多个字段存在重复的情况：

select * from tbl_order t where (t.order_no,t.order_desc) in (select t.order_no,t.order_desc from tbl_order t group by t.order_no,t.order_desc having count(*) > 1)

二.删除表中存在重复的记录
1.子查询方式

delete from tbl_order t
where (t.order_no,t.order_desc) in (select t.order_no,t.order_desc from tbl_order t group by t.order_no,t.order_desc having count(*) > 1)
and ROWID not in (select MIN(ROWID) from tbl_order t group by t.order_no,t.order_desc having count(*) > 1)

结果：

1 001
订单1

2 002 订单2

5 003 订单3

解释：第一个子查询查询出所有重复的记录，第二个子查询查出所有重复记录中最小的ROWID的记录，整个语句的作用是删除多条重复记录但保留一条ROWID最小的。

2.临时表方式

create table tmp as select distinct * from tbl_order;
truncate table tbl_order;
insert into tbl_order select * from tmp;