Question

In SQL Server, I have a column such as ID containing integers in descending order with one null value
ex.

ID
====
20
19
18
...
2
1
null

select id from mytable order by id desc

I need this to be ordered descending but null on top:

ID
====
null
20
19
18
...
2
1

The null is a result of a prior

union all

and needs to be there.
I had a few ideas, such as create an artificial large number.
Just want to see what your guys can come up with.
Have fun!

Answer 1

Use a CASE in your ORDER BY to force the NULLs first. This is supported by SQL Server.

SELECT
  id
FROM mytable
ORDER BY 
  CASE WHEN id IS NULL THEN 0 ELSE 1 END,
  id DESC

It works by deriving a “column” on which to sort that holds a 0 for NULL and 1 for everything else. The 0 sorts ahead of the 1. Then, we add the rest of the ORDER BY column chain to continue sorting, so adding id DESC forces the remaining rows (those with our derived 1) to sort in descending order by id.