SQL如何删除多余数据行的存储过程实例

1. --缘由：要把数据库给别人，但每表中的纪录最多只想给3条，于是要删除多余数据行

2. --注意：为避免数据参照导致删除出问题，建议先删除原有外键。

3. --存储过程spDeleteData，删除表名参数所对应的表的纪录，最多保留3条纪录

4. --set rowcount 、动态SQL、全局临时表的应用

5.

6. create proc spDeleteData(@tn nvarchar(30)) as

7. begin

8. set nocount on

9. if object_id('tempdb..##t') is not null drop table ##t

10. exec('select count(*) cnt into ##t from ' + @tn)

11. declare @row int

12. select @row=cnt from ##t

13. if @row>3

14. begin

15. set @row=@row-3

16. set rowcount @row

17. exec('delete from ' + @tn)

18. set rowcount 0

19. end

20. end

21.

22. go

23.

24. --存储过程spDeleteDataByTableName，调用spDeleteData删除数据库中所用表的纪录，每表最多保留3条纪录

25. --set rowcount 、while循环、局部临时表的应用

26.

27. create proc spDeleteDataByTableName as

28. begin

29. if object_id('tempdb..#t') is not null drop table #t

30. select [name] into #t from sysobjects where type='u'

31. declare @tn nvarchar(30)

32. set rowcount 1

33. select @tn=[name] from #t

34. while @@rowcount>0

35. begin

36. exec spDeleteData @tn --嵌套调用存储过程spDeleteData

37. select @tn=[name] from #t

38. delete from #t

39. end

40. set rowcount 0

41. end

42.

43. go

44.

45. exec spDeleteDataByTableName--调用存储过程spDeleteDataByTableName