my understanding of one to many relationship is joining a PK table with a FK table. and one to one relationship is joining two PK tables. is this accurate?

I need clarification...

plz

No. 1:1 still uses PK/FK, but you can choose to use the FK as the PK in the other table (not sure why you'd do that).

There are very few good reasons for a 1:1. They usually relate to implementing polymorphism or compensating for someone else's bad design (not a really good reason IMHO).