Using If else in SQL Select statement

Question

I have a select statement which will return 2 columns.

ID | IDParent

Then in my program I have to test if IDParent is < 1 then use

Answer 1

You can also use a union construct. I'm not sure if CASE is a common SQL construct ...

SELECT ID FROM tabName WHERE IDParent<1 OR IDParent IS NULL
UNION 
SELECT IDParent FROM tabName WHERE IDParent>1