1.用rowid方法
2.用group by方法
3.用distinct方法
1。用rowid方法
據據oracle帶的rowid屬性,進行判斷,是否存在重復,語句如下:
查數據:
select * from table1 a where rowid !=(select max(rowid)
from table1 b where a.name1=b.name1 and a.name2=b.name2......)
刪數據:
delete from table1 a where rowid !=(select max(rowid)
from table1 b where a.name1=b.name1 and a.name2=b.name2......)
2.group by方法
查數據:
select count(num), max(name) from student --列出重復的記錄數,並列出他的name屬性
group by num
having count(num) >1 --按num分組後找出表中num列重復,即出現次數大於一次
刪數據:
delete from student
group by num
having count(num) >1
這樣的話就把所有重復的都刪除了。
3.用distinct方法 -對於小的表比較有用
create table table_new as select distinct * from table1 minux
truncate table table1;
insert into table1 select * from table_new;