ER

Question 1

Attributes

Answer 1

Property of an entity

Question 2

Entity

Answer 2

A collection of attributes

Question 3

Domain

Answer 3

Set of values for an attribute

Question 4

Multi-valued Attribute

Answer 4

A list of attributes {7734, Plumb Rd, Galena, Oh, 43021}

Question 5

Composite Attribute

Answer 5

An organized list of attributes {Name} -> {Gabe, Steppers}

Question 6

Derived Attributes

Answer 6

Not stored, but calculated on request

Question 7

Cardinality

Answer 7

Relationships:

1:1, 1:n, m:n

Employee –N– —–1—- Project

The project can have many employees.
The employee can have one project.

Question 8

Total Participation

Answer 8

Means that the entity MUST be present.

For Chen Notation this is represented by double lines on the side of participation (opposite of carnality)

Question 9

Weak Entities

Answer 9

Cannot be identified on their own, dependent on a strong entity. Can have partial keys.

Question 10

Binary Relationship

Answer 10

Employee —-n—– ——1—— Project

Single mapping between employee and project

Question 11

Ternary Relationship

Answer 11

Employee —-n—— ——1—–Project
|
|
|
Salary

More thing two mappings in a relationship, should be shied away from