Question

For the following questions, select the correct answers.

6) Suppose we have a multiplicity where the first number is 0. What does this mean?

1. Existence (weak entities are inherently rare)
2. Its own primary key
3. Attributes
4. A purpose for existing in the diagram

8) Suppose that we have a diagram where an entity box points to itself. What can we say about this relationship?

1. None of these
2. It is a simple relationship
3. It is an irregular relationship
4. It is a recursive relationship

9) Suppose we have two entity boxes connected by two lines. What can we say about these entities?

1. There are two different relationships between the entities
2. There is no relationship between the entities (this notation is strictly for reference ONLY)
3. This is invalid in an ERD
4. There is only one extra-important relationship between the entities

10) Which of these symbols means “any number” in multiplicity?

1. *
2. 1
3. A triangle
4. 0

Answer 1

6) a) Existence

Explanation: Zero as the first number in the multiplicity refers to the existence of the relation.

7) d) It is a recursive relationship

Explanation: An arrow to itself is an example of self relationship.

8) C) This is invalid in an ERD

Explanation: Two entities/boxes cannot be connected by double lines. A double line can exist between a relationship and an entity which signifies weak relationshio.

9) a) *