一张表里面以两个字段为唯一字段，当几条记录的这两个字段完全相同时，需要删除重复项，如下表 a b c d 1 2 3 4 1 5 3 5 1 2 7 9 以a、b为唯一字段，第一条和第三条的a、b完全相同，所以，需要删除第一条记录1 2 3 4 或者第三条记录1 2 7 9 即如下结果： a b c d 1 2 3 4 1 5 3 5 或 a b c d 1 5 3 5 1 2 7 9
请问各位大侠这种sql语句怎么写
CREATE TABLE Tb1(id int, [a] varchar(255), [b] varchar(255), [c] varchar(255), [d] varchar(255)) INSERT Tb1(id, [a], [b], [c], [d]) SELECT 1, '1','2','3','4' UNION ALL SELECT 2, '1','5','3','5' UNION ALL SELECT 3, '1','2','7','9' UNION ALL SELECT 4, '1','4','7','6'
delete Tb1 where [id] not in (select max([id]) from Tb1 group by a,b ) select * from tb1
drop table tb1
如果要同时删除第一和第三行 即如下结果： a b c d 1 5 3 5
语句如下：
delete m from tb t inner join ( select a ,b from tb group by a , b having count(*)>1 )n on m.a = n.a and m.b = n.b 或 delete * from tb as m, ( select a ,b from tb group by a , b having count(*)>1 )n where m.a = n.a and m.b = n.b
------------------------------------------------------------------------------------ 在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢?谢谢! 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)
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 ------------------------------------------------------------------------------------------------ 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） select * from tablename where id in ( select id from tablename group by id having count(id) > 1)
