sql 語句刪除主鍵、更改主鍵、重複資料刪除列（多列組合），sql多列

sql 語句刪除主鍵、更改主鍵、重複資料刪除列（多列組合），sql多列
--alter table HistoryData drop constraint PK_HistoryData
alter table HistoryData add constraint PK_HistoryData primary key (CollectionTime,Code)
更改主鍵


delete from HistoryData where CollectionTime between'2014-09-01 00:00:00' and '2014-11-01 00:00:00'and ID not in ( 
select id from (
select Code,CollectionTime,max(ID) id from HistoryData 
where CollectionTime between'2014-09-01 00:00:00' and '2014-11-01 00:00:00'group by Code,CollectionTime) a)
重複資料刪除的列。