数据库中查询及删除重复记录的方法大全

旧城等待， 2022-08-27 08:53 198阅读 0赞

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)

select \* from gzseed\_im\_pic\_zan a where(a.imid,a.picurl) in (select imid,picurl from gzseed\_im\_pic\_zan group by imid,picurl 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)

delete  from gzseed\_im\_pic\_zan a where(a.imid,a.picurl) in (select imid,picurl from gzseed\_im\_pic\_zan group by imid,picurl having count(\*)>1)

and id not in (select min(id) from gzseed\_im\_pic\_zan group by   imid,picurl having count(\*)>1 );

delete from  gzseed\_im\_pic\_zan a where (a.imid,a.picurl ) in (select   imid,picurl  from  gzseed\_im\_pic\_zan  group by   imid,picurl  having count(\*) > 1)  
and id not in (select min(id) from  gzseed\_im\_pic\_zan  group by imid,picurl having count(\*)>1)

执行上面的报语法错误

delete from gzseed\_im\_pic\_zan where (imid,picurl ) in (select  imid,picurl  from gzseed\_im\_pic\_zan  group by  imid,picurl  having count(\*) > 1)  
and id not in (select min(id) from gzseed\_im\_pic\_zan  group by imid,picurl having count(\*)>1);

执行上面的报错：

You can't specify target table 'gzseed\_im\_pic\_zan' for update in FROM clause

原因：

修改或者删除数据表的数据，判断条件不能再从同一个表中select ；创建临时表解决

复制一张表

复制数据到新表

drop table if EXISTS gzseed\_im\_pic\_zan\_temp;  
/\*复制表结构\*/  
 create table gzseed\_im\_pic\_zan\_temp select \* from gzseed\_im\_pic\_zan where 1=2;  
/\*复制表数据\*/  
insert into gzseed\_im\_pic\_zan\_temp select \* from gzseed\_im\_pic\_zan;  
  
  
/\*如果有重复记录，就删除重复的记录，保留记录中最早的记录\*/   
 delete  from gzseed\_im\_pic\_zan  where ( imid, picurl) in (select b.imid,b.picurl from gzseed\_im\_pic\_zan\_temp b group by b.imid,b.picurl having count(\*)>1)  
  and id not in (select min(id) from gzseed\_im\_pic\_zan\_temp group by  imid,picurl 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