sql语句处理系统空值

[wab_94496491]

假如我有个字段 TimeOfDate
TimeOfDate
1984-4-5

1999-4-2

1998-6-4
TimeOfDate字段有五个记录：三个有时间，还有两个为空值（System.DBNULL.Value)
请问怎么用sql语句得到空值记录和另外两个较小的时间记录

[du9232]

where TimeOfDate is null 得到为空的记录

[hamadou]

select * from a_date where adate is null
or id in (select top 2 id from a_date order by adate desc)

[hamadou]

对于NULL值的判断方法是=还是IS，可以参看设置SET ANSI_NULLS

[ConanKid]

如果就是这样固定的格式，是很简单的。
select top 4 *
from 表名
order by timeofdate

[malingxian]

select * from [table] where TimeOfDate is null

[ConanKid]

闵峰：select * from a_date where adate is null
or id in (select top 2 id from a_date order by adate desc)
这个是取出时间较大的两个，可以改一下，从而取得较小的两个：
select * from time1 where timeofdate is null
or id in (select top 2 id from time1 where timeofdate is not null order by timeofdate)