ORACLE查詢及刪除重複記錄的方法

(一) ­

1、查找表中多餘的重複記錄，重複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) > 1) ­
­
2、刪除表中多餘的重複記錄，重複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) > 1) ­

and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1) ­

3、查找表中多餘的重複記錄（多個字段） ­

select * from vitae a ­

where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) ­­

4、刪除表中多餘的重複記錄（多個字段），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、查找表中多餘的重複記錄（多個字段），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 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 ­
­
　　有兩個意義上的重複記錄，一是完全重複的記錄，也即所有字段均重複的記錄，二是部分關鍵字段重複的記錄，比如Name字段重複，而其他字段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。 ­­

圖片　　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 tableName ­­
drop table tableName ­
­
select * into tableName from #Tmp ­
­
drop 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 ­
­
　　假設有重複的字段爲Name,Address，要求得到這兩個字段唯一的結果集 ­­

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) ­­

　　最後一個select即得到了Name，Address不重複的結果集（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) ­

查詢重複 ­­
select * from tablename where id in ( ­­
select id from tablename ­­
group by id ­­
having count(id) > 1 ­
­)­