IHP: How to fetch IS NULL rows from database?

Question

How to fetch first from all IS NULL rows from database?

Ex: Task-UserID

1-9

2-5

3-NULL

4-NULL

I would like to request database to fetch: 3 NULL <- and assign a user to the task 3

With this: |> filterWhereSql (#UserID, "IS NULL")

It is now working fine.