SQL “select where not in subquery” returns no results

Question

Disclaimer: I have figured out the problem (I think), but I wanted to add this issue to Stack Overflow since I couldn\'t (easily) find it anywhere. Also, someone might

Answer 1

select *,
(select COUNT(ID)  from ProductMaster where ProductMaster.CatID = CategoryMaster.ID) as coun 
from CategoryMaster