数据库重复数据
2015-10-09 19:26
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查询有重复数据的记录 select * from F group by a,b,c,d having count(*)>1
删除重复一模一样的记录,只保留一条记录
<span style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif;line-height:18px">select distinct * into #Tmp from tableName</span><br style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px" /><span style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif;line-height:18px">drop table tableName</span><br style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px" /><span style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif;line-height:18px">select * into tableName from #Tmp</span><br style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px" /><span style="font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif;line-height:18px">drop table #Tmp</span>
<h2 style="margin:0px; font-size:12px; color:rgb(68,68,68); font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif"><a target=_blank target="_blank" id="cb_post_title_url" class="singleposttitle" href="http://www.cnblogs.com/sunxiaonan/archive/2009/11/24/1609439.html" style="color:rgb(34,51,85)">SQL删除重复数据方法</a></h2>
<p style="margin:10px auto; font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px">例如: id name value 1 a pp 2 a pp 3 b iii 4 b pp 5 b pp 6 c pp 7 c pp 8 c iii id是主键 要求得到这样的结果 id name value 1 a pp 3 b iii 4 b pp 6 c pp 8 c iii</p><p style="margin:10px auto; font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px">方法1 delete YourTable where [id] not in ( select max([id]) from YourTable group by (name + value)) 方法2 delete a from 表 a left join( select id=min(id) from 表 group by name,value )b on a.id=b.id where b.id is null 查询及删除重复记录的SQL语句 查询及删除重复记录的SQL语句 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)</p><p style="margin:10px auto; font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px">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</p><p style="margin:10px auto; font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px">(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</p><p style="margin:10px auto; font-family:Verdana,'Lucida Grande',Arial,Helvetica,sans-serif; line-height:18px">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 )</p>
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