一张人员表（表名：Person），若想将姓名、身份证号、住址这三个字段完全相同的记录查找出来，sql语句如下：
复制代码 代码示例:
SELECT p1.*
FROM persons p1,persons p2
WHERE p1.id<>p2.id
AND p1.cardid = p2.cardid
AND p1.pname = p2.pname
AND p1.address = p2.address
下面，我们切入正题吧，介绍删除重复记录的方法。
在sql server中删除重复记录，可以参考如下的几种方法：
1，rowid方法
2，group by方法
3，distinct方法
下面我们分别来介绍，并举一些例子，供大家参考。
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：
复制代码 代码示例:
---查询数据:
select * from table1 a where rowid !=(select max(rowid)
from table1 b where a.name1=b.name1 and a.name2=b.name2......)
---删除数据：
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
复制代码 代码示例:
---查询数据:
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
---删除数据：
delete from student
group by num
having count(num) >1
---删除所有重复记录。
3，用distinct方法 -对于小的表比较有用
复制代码 代码示例:
create table table_new as select distinct * from table1 minux
truncate table table1;
insert into table1 select * from table_new;
附，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
复制代码 代码示例:
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
复制代码 代码示例:
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）
复制代码 代码示例:
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
复制代码 代码示例:
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)
