select from category and any sub category

I have a simple catalogue running. Products are inside basic high level categories..  I select items from this based on this ID. 

For example: SELECT * FROM products WHERE cateogryId = ?

However, I’ve now been asked to add sub categories.

So, if I had Cars before, I now have Cars > Toyota > 4WD

Cars: 2
Toyota: 34 (Parent 2)
4WD: 23 (Parent 34)

Now when I select ID 2, I want to also select those within 34 & 23..

How can I do this?