Rob & Coronell - Chapter 3.6

Question 1

Which relationship can be found in a good relational database?

Answer 1

1: 1:M relationship
2. 1:1 Relationship

M:N -> not used in this type of database.

Question 2

How is a 1:M relationship easily implemented?

Answer 2

By putting the primary key of the 1 side in the table of the many side as a foreign key.

Question 3

What does a 1:1 relationship ensure?

Answer 3

That two entity sets are not placed in the same table when they should not be.

Question 4

Why is a 1:1 relationship not common in a good relational database?

Answer 4

It might indicate that the entity components are not defined properly -> could indicate that the two entities actually belong in the same table.

Question 5

What is a composite entity?

Answer 5

An entity (table) that is created to link the tables that were originally related in an M:N relationship.

• > Should include the primary keys of the tables that are to be linked (as foreign keys).
• Also known as: bridge entity, associative entity, linking table