Chapter 4 Flashcards
Identifiers
One or more attributes that uniquely identify each entity instance. Basically a primary key in ERM
Composite identifier
An identifier with one or more attribute
Composite attribute
An attribute which can be further divided into more attributes. Like address -> street,city,state,zip
Simple attribute
An attribute that cannot be subdivided
Single-valued attribute
an attribute that can have only one single value such as social security code
Muti-valued attribute
An attribute which can have many values such as college_degree
Derived attribute
An attribute whose value is calculated(derived) from another value, such as age is derived from date of birth
Participants
Entities which participate in a relationship
Connectivity
Describes the relationship classification
Cardinality
Expresses the minimum and maximum number of entity occurrences associated with related entities
Existence-dependent
An entity which was exist in the database only when it is associated with another related entity occurrence
Existence-independent
An entity which can exists apart from all of its related entities. Referred to as a strong entity
Weak relationship (Non-identifying)
Exists when the PK of the related entity does not contain the PK component of the parent entity
Strong (Identifying) relationship
Exists when the PK of the related entity contains a PK component of the parent entity
relationship degree
Indicates the number of entities or participants associated with a relationship
