sql 查出一張表中重復(fù)的所有記錄數(shù)據(jù)
1互订、在面試的時(shí)候碰到一個(gè) 問題，就是讓寫一張表中有id和name 兩個(gè)字段溃卡，查詢出name重復(fù)的所有數(shù)據(jù)西疤，現(xiàn)在列下：
select * from xi a where(a.username) in ( select username from xi group by username having count(*)>1)
2、查詢出所有數(shù)據(jù)進(jìn)行分組之后夯缺，和重復(fù)數(shù)據(jù)的重復(fù)次數(shù)的查詢數(shù)據(jù)蚤氏，先列下：
select count(username) as'重復(fù)次數(shù)',username from xi group by username having count(*)>1 order by username desc
3、一下為 查看別人的 結(jié)果踊兜，現(xiàn)列下：查詢及刪除重復(fù)記錄的方法大全
1竿滨、查找表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)單個(gè)字段（peopleId）來判斷
select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId)>1)
2捏境、刪除表中多余的重復(fù)記錄于游，重復(fù)記錄是根據(jù)單個(gè)字段（peopleId）來判斷，只留有rowid最小的記錄
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垫言、查找表中多余的重復(fù)記錄（多個(gè)字段）?
select * from vitae a where (a.peopleId, a.seq)? in (select peopleId, seq from vitae group by peopleId , seq having count(*)>1)
4贰剥、刪除表中多余的重復(fù)記錄（多個(gè)字段），只留有rowid最小的記錄
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筷频、查找表中多余的重復(fù)記錄（多個(gè)字段）蚌成，不包含rowid最小的記錄
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)
比方說前痘，在A表中存在一個(gè)字段“name”，而且不同記錄之間的“name”值有可能會相同笑陈，現(xiàn)在就是需要查詢出在該表中的各記錄之間际度，“name”值存在重復(fù)的項(xiàng)；
Select Name,Count(*) From A Group By Name Having Count(*)>1
如果還查性別也相同大則如下:
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(*) >;
open cur_rows fetch cur_rows into @id,@maxwhile @@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,@maxend
close cur_rows
set rowcount 0
方法二涵妥、
＂重復(fù)記錄＂有兩個(gè)意義上的重復(fù)記錄乖菱，一是完全重復(fù)的記錄，也即所有字段均重復(fù)的記錄蓬网，二是部分關(guān)鍵字段重復(fù)的記錄窒所，比如Name字段重復(fù)，而其他字段不一定重復(fù)或都重復(fù)可以忽略帆锋。
1吵取、對于第一種重復(fù)，比較容易解決锯厢，使用
select distinct * from tableName
就可以得到無重復(fù)記錄的結(jié)果集皮官。
如果該表需要刪除重復(fù)的記錄（重復(fù)記錄保留1條），
可以按以下方法刪除
select distinct * into #Tmp from tableName
drop table tableName select * into tableName from #Tmp
drop table #Tmp
發(fā)生這種重復(fù)的原因是表設(shè)計(jì)不周產(chǎn)生的实辑，增加唯一索引列即可解決捺氢。
2、這類重復(fù)問題通常要求保留重復(fù)記錄中的第一條記錄剪撬，操作方法如下 假設(shè)有重復(fù)的字段為Name,Address摄乒，要求得到這兩個(gè)字段唯一的結(jié)果集
select identity ( int,1,1) as autoID,* into #Tmp from tableName
select min ( autoID ) as auto ID into #Tmp2 from #Tmp groupby Name,autoID
select * from #Tmp where autoID in? ( select autoID from? #tmp2)
最后一個(gè)select即得到了Name，Address不重復(fù)的結(jié)果集（但多了一個(gè)autoID字段残黑，實(shí)際寫時(shí)可以寫在select子句中省去此列）
(四)
查詢重復(fù)
select * from tablename where id in ( select id from tablename group by id having count(id)>1)
