Intro to DataBase Chapter 4

Single-valued

A single-valued attribute is an attribute that can have only a single value. For example, a person can have only one Social Security number, and a manufactured part can have only one serial number.

Define entity, attribute and relationship

An entity is an object of interest to the end user. Attributes are characteristics of entities. A relationship is an association between entities.

Explain attributes domain

Attributes have a domain, a domain is the set of possible values for a given attribute. For example, the domain for the grade point average (GPA) attribute is written (0,4) because the lowest possible GPA value is 0 and the highest possible value is 4.

Multivalued

Multivalued attributes are attributes that can have many values. For instance, a person may have several college degrees, and a household may have several different phones, each with its own number.

What are the three types of relationship?

Relationships may be classified as one-to-one, one-to-many, or many-to-many.