查詢及刪除重復記錄

　　(一)
查找表中多余的重復記錄重復記錄是根據單個字段（peopleId）來判斷
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > )
刪除表中多余的重復記錄重復記錄是根據單個字段（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) > )
and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>)
查找表中多余的重復記錄（多個字段）
select * from vitae a
where (apeopleIdaseq) in (select peopleIdseq from vitae group by peopleIdseq having count(*) > )
刪除表中多余的重復記錄（多個字段）只留有rowid最小的記錄
delete from vitae a
where (apeopleIdaseq) in (select peopleIdseq from vitae group by peopleIdseq having count(*) > )
and rowid not in (select min(rowid) from vitae group by peopleIdseq having count(*)>)

　　查找表中多余的重復記錄（多個字段）不包含rowid最小的記錄
select * from vitae a
where (apeopleIdaseq) in (select peopleIdseq from vitae group by peopleIdseq having count(*) > )
and rowid not in (select min(rowid) from vitae group by peopleIdseq having count(*)>)
(二)
比方說
在A表中存在一個字段“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”值存在重復的項
Select NameCount(*) From A Group By Name Having Count(*) >
如果還查性別也相同大則如下:
Select Name*Count(*) From A Group By Name* Having Count(*) >

　　(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@max
while @@fetch_status=
begin
select @max = @max
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id@max
end
close cur_rows
set rowcount
　　方法二
　　有兩個意義上的重復記錄一是完全重復的記錄也即所有字段均重復的記錄二是部分關鍵字段重復的記錄比如Name字段重復而其他字段不一定重復或都重復可以忽略
　　對於第一種重復比較容易解決使用
select distinct * from tableName
　　就可以得到無重復記錄的結果集
　　如果該表需要刪除重復的記錄（重復記錄保留條）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
　　發生這種重復的原因是表設計不周產生的增加唯一索引列即可解決
　　這類重復問題通常要求保留重復記錄中的第一條記錄操作方法如下
　　假設有重復的字段為NameAddress要求得到這兩個字段唯一的結果集
select identity(int) as autoID * into #Tmp from tableName
select min(autoID) as autoID into #Tmp from #Tmp group by NameautoID
select * from #Tmp where autoID in(select autoID from #tmp)
　　最後一個select即得到了NameAddress不重復的結果集（但多了一個autoID字段實際寫時可以寫在select子句中省去此列）
(四)
查詢重復
select * from tablename where id in (
select id from tablename
group by id
having count(id) >
)
查找表中多余的重復記錄（多個字段）
select * from vitae a
where (apeopleIdaseq) in (select peopleIdseq from vitae group by peopleIdseq having count(*) > )
運行會產生問題where(apeopleIdaseq)這樣的寫發是通不過的！！！

From:http://tw.wingwit.com/Article/program/MySQL/201311/29563.html