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 代码如下:
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 代码如下:
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 代码如下:
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 代码如下:
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
复制代码 代码如下:
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;
复制代码 代码如下:
select name,count(*) from a group by name having count(*) > 1
如果还查性别也相同大则如下:
复制代码 代码如下:
select name,sex,count(*) from a group by name,sex having count(*) > 1
(三)
方法一
复制代码 代码如下:
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
复制代码 代码如下:
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
复制代码 代码如下:
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
复制代码 代码如下:
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
复制代码 代码如下:
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1
)