SQL重复记录查询

你的名字 2021-09-11 04:10 431阅读 0赞

SQL重复记录查询  
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,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录（多个字段），不包含rowid最小的记录  
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

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)