select * from xi a where (a.username) in  (select username from xi group by username  having count(*) > 1)

2、查詢出所有資料進行分組之後，和重複資料的重複次數的查詢資料，先列下：

select  count(username) as '重複次數',username from xi group by username  having count(*)>1 order by username desc

3、一下為 檢視別人的 結果，現列下：查詢及刪除重複記錄的方法大全

1、查詢表中多餘的重複記錄，重複記錄是根據單個欄位（peopleId）來判斷select * from people
where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1)

2、刪除表中多餘的重複記錄，重複記錄是根據單個欄位（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、查詢表中多餘的重複記錄（多個欄位） 
select * from vitae a
where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq  having count(*) > 1)

4、刪除表中多餘的重複記錄（多個欄位），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、查詢表中多餘的重複記錄（多個欄位），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
在A表中存在一個欄位“name”，
而且不同記錄之間的“name”值有可能會相同，
現在就是需要查詢出在該表中的各記錄之間，“name”值存在重複的項；
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 integerdeclare cur_rows cursor local for select 主欄位,count(*) from 表名 group by 主欄位 having count(*) >； 1open cur_rowsfetch cur_rows into @id,@maxwhile @@fetch_status=0beginselect @max = @max -1set rowcount @maxdelete from 表名 where 主欄位 = @idfetch cur_rows into @id,@maxendclose cur_rowsset rowcount 0

方法二＂重複記錄＂有兩個意義上的重複記錄，一是完全重複的記錄，也即所有欄位均重複的記錄，二是部分關鍵欄位重複的記錄，比如Name欄位重複，而其他欄位不一定重複或都重複可以忽略。

　　1、對於第一種重複，比較容易解決，使用select distinct * from tableName　　就可以得到無重複記錄的結果集。　　如果該表需要刪除重複的記錄（重複記錄保留1條），可以按以下方法刪除select distinct * into #Tmp from tableNamedrop table tableNameselect * into tableName from #Tmpdrop table #Tmp　　發生這種重複的原因是表設計不周產生的，增加唯一索引列即可解決。

　　2、這類重複問題通常要求保留重複記錄中的第一條記錄，操作方法如下　　假設有重複的欄位為Name,Address，要求得到這兩個欄位唯一的結果集select identity(int,1,1) as autoID, * into #Tmp from tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoIDselect * from #Tmp where autoID in(select autoID from #tmp2)　　最後一個select即得到了Name，Address不重複的結果集（但多了一個autoID欄位，實際寫時可以寫在select子句中省去此列）

(四)
查詢重複select * from tablename where id in (select id from tablenamegroup by idhaving count(id) > 1)