DBMS Chapter 7 Flashcards
Three Components of ERD
Entity Relationship Attributes
What are Entities
specific objects or things in the mini-world that are represented in the database. *a specific entity will have a value for each attribute
What are Attributes
properties used to describe an entity.
What are the types if Attributes
Simple Composite Multi-valued *note:composite and multi-valued may be nested arbitrarily to any number of levels although its rare.
Define Simple Attributes
each entity has a single atomic value for the attributes
Define Composite Attributes
Attribute may be composed of several components
Define Multi-valued Attributes
entity may have multiple values for the attributes
Define Key Attributes
An attribute of an entity type for which each entity must have a unique value is
Define Entity Type
Entities with the same basic attributes are grouped or typed into an entity type
Define Attribute Domain
Each simple attribute of an entity type is associated with domain of values
Define Relationships
relates two or more distinct entities with a specific meaning
Relationship Type
Relationships of the same type are grouped or typed into a relationship type
Degree of a Relationship Type
the number of participating entity types
Entity Type
Weak Entity Type
Relationship type
Identifying Relationship Type
Attribute
Key Attribute
Multivalued Attribute
Composite Attribute
Derived Attribute
Total Participation of E2 in R
Cardinality Ratio 1:N for E1:E2 in R
Structural Constraint (min, max) on participation of E in R
