SQL语句的简单问题

[ba_saner]

有表

id scale
1 5
2 6
3 4
4
5 7
6 4
7
8 12
9 7

select top 4 * from table order by abs(scale-8)

执行后为什么是7，4，9，5行？如何才能不包括4，7行？
4，7行的scale是NULL

[gmlxf]

select top 4 * from table order by abs(scale-8) where scale is not null

[gmlxf]

sql中是用
where col1 is null
来判断

不能是
where col1=null

[ba_saner]

select top 4 * from table order by abs(scale-8) where scale is not null

select top 4 * from table where scale is not null order by abs(scale-8)

以上两个句子那个正确？

[DigJim]

或者

select top 4 * from table order by abs(scale-8) where ISNULL(scale ,'') <> ''

[gmlxf]

刚才写错了是：
select top 4 * from table where scale is not null order by abs(scale-8)

[shenanigan]

select top 4 * from table where scale is not null order by abs(scale-8)
这句正确