1. Entity - Relationship Modelling Exercises by Artem Chebotko

2. Exercise 1
Draw an ER diagram and translate it to the relational model for the following:
A customer orders at least one book from a bookstore.
A bookstore can process (orders from) many (or none) customers.
A book can be ordered many (or zero) times.

3. Exercise 2
Draw an ER diagram and translate it to the relational model for the following:
A customer places at least one order.
An order is placed by exactly one customer.
An order is sent to exactly one bookstore.
A bookstore handles many (or none) orders.
An order includes at least one book.
A book can be included in many (or zero) orders.

4. Exercise 3
Draw an ER diagram and translate it to the relational model for the following:
An animal shelter has many (or none) pets.
A pet can be a cat or a dog. No other kinds of animals are allowed in a shelter.
A pet is characterized by a tag (unique id), name, breed, age, coat, pattern, and weight.

5. Exercise 4
Draw an ER diagram and translate it to the relational model for the following:
An animal shelter has many (or none) pets.
A pet can be a cat or a dog. No other kinds of animals are allowed in a shelter.
A pet is characterized by a tag (unique id), name, breed, age, coat, pattern, and weight. In addition, height and other size characteristics are recorded for dogs and food preferences are recorded for cats.
A dog is walked by a volunteer at least twice a day.

6. Exercise 5
Draw an ER diagram and translate it to the relational model for the following:
An animal shelter has many (or none) pets.
A pet can be a cat or a dog. Occasionally, a shelter hosts other kinds of animals (deer, raccoon, bird, etc.) that may require medical (veterinarian) treatment.
A pet is characterized by a tag (unique id), name, breed, age, coat, pattern, and weight.

7. Exercise 6
Draw an ER diagram and translate it to the relational model for the following:
A computer programmer in a software development company is described by an employee id, name, phone, address, , and set of skills (non-empty set).
A programmer works on many (or none) projects.
A project has at least one programmer assigned to it.
A project has a name, description, and set of skills (non-empty set) required to contribute to it.

8. Exercise 7
Draw an ER diagram and translate it to the relational model for the following:
A university offers a number of courses.
A course may have one or more (or none) courses as prerequisites.
A course may or may not have one or more scheduled sections.
A professor teaches at least one course section.
A student is enrolled in at least three and at most seven course sections.
A professor assigns grades to students enrolled in a course section that s/he teaches.

9. Exercise 8
Draw an ER diagram and translate it to the relational model for the following:
A bank offers three types of accounts: checking, savings, and loan/credit.
A checking account has account-number, date-opened, balance, and service-fee.
A savings account has account-number, date-opened, balance, and interest-rate.
A loan/credit account has account-number, date-opened, balance, service-fee, interest-rate, and credit-limit.