在本文中,我们主要介绍重复字段的内容,自我感觉有个不错的建议和大家分享下
查询及删除重复记载的SQL语句
1、查找表中多余的重复记载，重复记载是根据单个字段（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载，重复记载是根据单个字段（peopleId）来判断，只留有rowid最小的记载
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)
注:rowid为
自带不必该.....
3、查找表中多余的重复记载（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载（多个字段），只留有rowid最小的记载
delete from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by 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载（多个字段），不包括rowid最小的记载
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
(二)
比方说在A表中存在一个字段“name”，而且不同记载之间的“name”值有可能会雷同，
现在就是需要查询出在该表中的各记载之间，“name”值存在重复的项；
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也雷同大则如下:
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
＂重复记载＂有两个意义上的重复记载，一是完全重复的记载，也即全部字段均重复的记载，二是部分关键字段重复的记载，比如Name字段重复，而其他字段不一定重复或都重复可以疏忽。
1、对于第一种重复，比拟容易解决，应用
select distinct * from tableName
就能够得到无重复记载的结果集。 如果该表需要删除重复的记载（重复记载保留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发生的，增加独一索引列便可解决。
2、这类重复问题平日要求保留重复记载中的第一条记载，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独一的结果集
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，现实写时可以写在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)
=======================================
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 --列出重复的记载数，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
这样的话就把全部重复的都删除了。
3.用distinct方法 -对于小的表比拟有效
create table table_new as select distinct * from table1 minux
truncate table table1;
insert into table1 select * from table_new;
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