Sql ÀïÃæ ROW_NUMBER Ó¦Óó¡¾°

ROW_NUMBER ·µ»Ø°´Ò»¶¨¹æÔòÅÅÐòµÄµ±Ç°¼Ç¼¶ÔÓ¦µÄÐкÅ
±ÈÈçÎÒÃÇÓÐÕâÑùÒ»¸öÓ¦Óó¡¾°£º
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1.Ϊ´ËÎÒÃÇÒª½¨Á¢Ò»ÕűíÀ´±£´æ±¨Ãû²ÎÈüÕßµÄÐÕÃû¼°Æð±¨Ãûʱ¼ä
CREATE 
TABLE [dbo].[UserEnroll](
[UserName] [nvarchar]
(50) NULL, --²ÎÈüÕßµÄÐÕÃû
[EnrollTime] [datetime]
NULL --±¨Ãûʱ¼ä
) 
ON  [PRIMARY]
2.ÎÒÃÇSql Ïò±íÖвåÈëÊý¾Ý£¬Ä£Äâ²ÎÈüÕß±¨Ãû 
insert
  into [dbo].[UserEnroll] values('CC', GETDATE())
insert  into [dbo].[UserEnroll] values('CC1', DateAdd(DAY,-1,GETDATE()))
insert 
into [dbo].[UserEnroll] values('CC2', DateAdd(DAY,-2,GETDATE()))
insert 
into [dbo].[UserEnroll] values('CC3', DateAdd(DAY,-3,GETDATE()))
insert 
into [dbo].[UserEnroll] values('CC4', DateAdd(DAY,-4,GETDATE ()))
insert 
 into [dbo].[UserEnroll] values('CC5', DateAdd(DAY,-5,GETDATE()))
insert 
 into [dbo].[UserEnroll] values('CC6', DateAdd(DAY,-6,GETDATE()))
insert
 into [dbo].[UserEnroll] values('CC7', DateAdd(DAY,-7,GETDATE()))
 
3.ɾ³ý·Ç×îÔç5±¨ÃûµÄÈË
  a.  ¸ø±í¼ÓÉÏÐкÅ
SELECT
*, ROW_NUMBER() OVER(ORDER BY EnrollTime) AS RowNum
from [dbo].[UserEnroll]
   ½á¹ûÈçÏ£º
   UserName EnrollTime RowNum
CC7 2010-05-11 17:38:42.403 1
CC6 2010-05-12 17:38:42.403 2
CC5 2010-05-13 17:38:42.403 3
CC4 2010-05-14 17:38:42.403 4
CC3 2010-05-15 17:38:42.403 5
CC2 2010-05-16 17:38:42.403 6
CC1 2010-05-17 17:38:42.403 7
CC 2010-05-18 17:38:42.403 8
 b. ÄÇôÎÒÃÇɾ³ýRowNum ´óÓÚ5µÄ¼Ç¼
 
WITH UserEnrollWithRowNumber AS (
SELECT *, ROW_NUMBER() OVER(ORDER BY EnrollTime) AS
RowNum from [dbo].[UserEnroll])
DELETE from  UserEnrollWithRowNumber
WHERE RowNum >  5
½á¹ûΪ effect 3 rows
 c. ÔÙÓÃa²½ÖеÄÓï¾ä²éѯ±¨Ãû±í½á¹ûΪ
UserName EnrollTime RowNum
CC7 2010-0