1、第一種重復很容易解決，不同數據庫環境下方法相似：

MySQL

create table tmp select distinct * from tableName;

drop table tableName;

create table tableName select * from tmp;

drop table tmp;

SQL Server

select distinct * into #Tmp from tableName;

drop table tableName;

select * into tableName from #Tmp;

drop table #Tmp;

Oracle

create table tmp as select distinct * from tableName;

drop table tableName;

create table tableName as select * from tmp;

drop table tmp;

發生這種重復的原因是由于表設計不周而產生的，增加唯一索引列就可以解決此問題。

2、此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Name,Address，要求得到這兩個字段唯一的結果集

Mysql

alter table tableName add autoID int auto_increment not null;

create table tmp select min(autoID) as autoID from tableName group by Name,Address;

create table tmp2 select tableName.* from tableName,tmp where tableName.autoID = tmp.autoID;

drop table tableName;

rename table tmp2 to tableName;

SQL Server

select identity(int,1,1) as autoID, * into #Tmp from tableName;

select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,Address;

drop table tableName;

select * into tableName from #Tmp where autoID in(select autoID from #Tmp2);

drop table #Tmp;

drop table #Tmp2;

Oracle

DELETE FROM tableName t1 WHERE t1.ROWID > (SELECT MIN(t2.ROWID) FROM tableName t2 WHERE t2.Name = t1.Name and t2.Address = t1.Address);

說明：

1. MySQL和SQL Server中最后一個select得到了Name，Address不重復的結果集（多了一個autoID字段，在大家實際寫時可以寫在select子句中省去此列）

2. 因為MySQL和SQL Server沒有提供rowid機制，所以需要通過一個autoID列來實現行的唯一性，而利用Oracle的rowid處理就方便多了。而且使用ROWID是最高效的刪除重復記錄方法。