What is the best way to enforce a 'subset' relationship with integrity constraints

Question

For example, given 3 tables:

• gastropod
• snail
• slug

and assuming we want to enforce that

1. every row in \'gastropod\

Answer 1

I know this problem as a supertype/subtype issue. I've written about it several times on SO. In this post, it's presented as a solution to a problem with staff, customers, and suppliers. But this post has the most extended discussion behind the rationale and how the constraints work. It's written in terms of online publications.