删除重复记录的SQL语句
1.用rowid方法
2.用group by方法
3.用distinct方法
?
1。用rowid方法
据据Oracle带的rowid属性，进行判断，是否存在重复,语句如下：?
查数据:?
???? select * from table1 a where rowid !=(select?? max(rowid)???
???? from table1 b where a.name1=b.name1 and a.name2=b.name2......)?
删数据：?
??? 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
查数据:?
select count(num),max(name) from student --列出重复的记录数，并列出他的name属性?
group by num?
having count(num) >1 --按num分组后找出表中num列重复，即出现次数大于一次?
删数据：?
delete from student?
group by num?
having count(num) >1?
这样的话就把所有重复的都删除了。
3.用distinct方法?-对于小的表比较有用
create table table_new as?? select distinct *?? from table1 minux?
truncate table table1;?
insert into table1 select * from table_new;
?
查询及删除重复记录的方法大全?
1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断
select * from people?
where peopleId in (select? peopleId? from? people? group? by? peopleId? having? count(peopleId) > 1)
2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录?
delete from people?
where peopleId? in (select? peopleId? from people? group? by? peopleId?? having? count(peopleId) > 1)?
and rowid not in (select min(rowid) from? people? group by peopleId? having count(peopleId )>1)
3、查找表中多余的重复记录（多个字段）?
select * from vitae a?
where (a.peopleId,a.seq) in? (select peopleId,seq from vitae group by peopleId,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 vitae a?
where (a.peopleId,seq having count(*) > 1)?
and rowid not in (select min(rowid) from vitae group by peopleId,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 vitae a?
where (a.peopleId,seq having count(*)>1)
(二) 比方说 在A表中存在一个字段“name”，?
而且不同记录之间的“name”值有可能会相同，?
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；?
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也相同大则如下:?
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
(三) 方法一
declare @max integer,@id integer
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >； 1
open cur_rows
fetch cur_rows into @id,@max
while @@fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0
方法二
＂重复记录＂有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。
1、对于第一种重复，比较容易解决，使用
select distinct * from tableName
就可以得到无重复记录的结果集。
如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。
2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下
假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集
select identity(int,1,1) as autoID,* into #Tmp from tableName
select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
select * from #Tmp where autoID in(select autoID from #tmp2)
最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）
(四) 查询重复
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1)
