Is there a way to get the default components\ratings for a part if a category does not exist? And if the category does exist to get only those components ratings for that category?

Simiplified DB setup

A Part is has one or more components.

Components have one or more ratings.

Ratings of components for a part are grouped under a category.

A Catetgory are linked to the Part. There may be one or more categories for this part.


Is there one SQL statement that can

1. If I feed it an existing category, return only the components and ratings for that category. (Part is known)

2. If I feed it a non exisint category, return only the components with ratings of zero. (Part is known)


Thanks for any help

Bob