TSQL ORDER BY带有空的第一个或最后一个(在底部或顶部)

Question

我有一个日期列有一些NULL.我想按日期栏ASC订购,但我需要将NULLs放在底部.如何在TSQL上做到这一点？

Answer 1

在标准SQL中,您可以指定放置空值的位置:

order by col asc nulls first
order by col asc nulls last
order by col desc nulls first
order by col desc nulls last

但是T-SQL不符合这里的标准.NULL的顺序取决于您是在T-SQL中升序还是降序排序:

order by col asc -- implies nulls first
order by col desc -- implies nulls last

使用整数,您可以简单地按负数排序:

order by -col asc -- sorts by +col desc, implies nulls first
order by -col desc -- sorts by +col asc, implies nulls last

但是这对于日期(或者那个字符串)是不可能的,所以你必须首先排序为null /不是null,然后只有你的列:

order by case when col is null then 1 else 2 end, col asc|desc -- i.e. nulls first
order by case when col is null then 2 else 1 end, col asc|desc -- i.e. nulls last

Answer 2

Select *
 From  YourTable
 Order By case when DateCol is null then 0 else 1 end
         ,DateCol

甚至 Order By IsNull(DateCol,'2525-12-31')