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)
imid,picurl having count(*)>1
delete from gzseed_im_pic_zan a where (a.imid,a.picurl ) imid,picurl from gzseed_im_pic_zan group by imid,picurl
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
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
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
)