用SQL語句,刪除掉重複項只保留一條

在幾千條記錄裡,存在著些相同的記錄,如何能用SQL語句,刪除掉重複的呢
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 peopleName in (select peopleName from people group by peopleName having count(peopleName) > 1) 
and peopleId not in (select min(peopleId) from people group by peopleName having count(peopleName)>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)

6.消除一個欄位的左邊的第一位：

update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'

7.消除一個欄位的右邊的第一位：

update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

8.假刪除表中多餘的重複記錄（多個欄位），不包含rowid最小的記錄 
update vitae set ispass=-1
where peopleId in (select peopleId from vitae group by peopleId

來自：http://blog.csdn.net/anya/article/details/6407280/