In SQL what is the difference between a JOIN and a UNION? When will you use one instead of the other?

Section 5 – Create SQL queries based on the provided relational database schema:  

Foreign key.

Section 4 – Select True or False  

Retrieve all the borrower names and phones who has book loans from the branches located in Miami.

Conceptual Schema.

What is the difference between a primary key and a foreign key?

Section 3 – Multiple selection: For the following binary relationships, suggest cardinality ratios based on the common-sense meaning of the entity types.

Your cat needs 0.5 lb of protein per day. You go to the pet store and have two cat food options: Cat food A has 55% protein and Cat food B has 15% protein. How much Cat food A and Cat Food B would you have to feed your cat, per day, to meet its protein requirements?

List and explain three characteristics of the database approach.