Question

DATABASE MANAGEMENT SYSTEMS

After looking at the material in Section 2, go ahead and answer the following questions:

• What is a foreign Key? (1 Point)
• What is a composite attribute? Give an example (1 Points)
• What is a multivalued attribute? Give an example (1 Points)
• What is a relationship Modality? What is a relationship Cardinality? (2 Point)

(Make sure you understand the difference between the two)

• Open MySql workbench and build an ERD with the following Entities, Attributes and Relationships.

We want to track historical data of Soccer players. We want to track current data for clubs, Coaches and Soccer Balls.

A soccer player can only play for one club but over time a player would have played for one or many clubs. A club has many players.

Some players are Captains and supervise other players.

A club can have one or many Coaches, a Coach can only coach one team.

A Team has one or many soccer balls, a Soccer ball can only belong to one team. (10 Points)

Players	Teams	Coaches	Soccer Balls	To be defined
Player ID	Team ID	Coach ID	Serial Number	…..
First Name	Team Name	C_FirstName	Maker	…..
Last Name	City	C_LastName	Color	…..
Address1		Phone
City
State
Zip Code
Country of Origin

Answer 1

1. What is a foreign key?

Answer: - Foreign key is an attribute. Which establish relationship between any two (2) tables.

So, a foreign key is a field (or) collection of fields in one table that referes to the primary key in another table.

2. What is Composite attribute? Give an example

Answer: - Composite attribute means which can be divided into smaller sub parts.

Example: -

Explanation: -

• Student is an entity.
• Student have a name.
• Name is a attribute of student.
• So this Name is forther divided in to smaller sub parts:First_Name, Middle_Name and Last_Name.

So this is Composite Attribute. So the "Name" is call it as a composite attribute.

3. What is a multivalued attribute?Give an example

Answer: - Multivalue means multiple values can be derived. It may contains more than one value.

Example:- A person can have more then one phone number.

A person can have more then one E-mail address.

4. What is a relationship Modality? What is a relationship Cardinality?

Answer: -

relationship Modality:- Modality indicates the minumum number of times an instance in one entity can be associated with an instance in the related entity.

relationship Cardinality: - Cardinality indicates the maximum number of times an instance in one entity can be associated with instances in the related entity.

Simple explanation:- "Card" which means "number". it "shows how both the entities are connected with each other".

There are three(3) types:

1. one to one

2. one to many

3. many to many