02_04 ER Modeling Flashcards
An ER term for an association (relationship) between TWO entities.
For example, PROFESSOR teaches CLASS.
binary relationship
A property that assigns a specific value to connectivity and expresses the range of allowed entity occurrences associated with a single occurrence of the related entity.
cardinality
An attribute that can be further subdivided to yield additional attributes.
For example, a phone number such as 615-898-2368 may be divided into an area code (615), and exchange number (898), and a four-digit code (2368).
composite attribute
Compare to simple attribute
In ER modeling, a key composed of more than one attribute.
composite identifier
The type of relationship between entities.
connectivity
An attribute that does not physically exist and is derived via an algorithm.
For example, the Age attribute might be derived by subtracting the birth data from the current date.
derived attribute
A property of an entity whose existence depends on one or more other entities.
existence-dependent
In such an environment, the existence-independent table must be created and loaded first because the existence-dependent key cannot reference a table that does not yet exist.
A property of an entity that can exist apart from one or more related entities.
existence-independent
Such a table must be created first when referencing an existence-dependent table.
One or more attributes that uniquely identify each entity instance.
identifier
A process based on repetition of steps and procedures.
iterative process
A relationship in which one entity must have a corresponding occurrence in another entity.
mandatory participation
An attribute that can have many values for a single entity occurrence.
For example, an EMP_DEGREE attribute might store the string “BBA, MBA, PHD” to indicate three different degrees held.
multivalued attribute
In ER modeling, a condition in which one entity occurrence does not require a corresponding entity occurrence in a particular relationship.
optional participation
In ER modeling, an attribute that does not require a value.
It can be left empty.
optional attribute
An ER term for entities that participate in a relationship.
participants
For example, in the relationship “PROFESSOR teaches CLASS,” the teaches relationship is basedo nthe participants PROFESSOR and CLASS.
A relationship found within a single entity type.
For example, an EMPLOYEE is married to an EMPLOYEE or a PART is a component of another PART.
recursive(unary) relationship
An entity that is existence-independent.
strong entity (regular entity)
The organization of a relational database as described by the database administrator.
relational schema
The number of entities or participants associated with a relationship.
Can be unary, binary, ternary, or higher.
relationship degree
In ER modeling, an attribute that must have a value.
It cannot be left empty.
required attribute
An attribute that cannot be subdivided into meaningful components.
simple (atomic) attribute
Compare to composite attribute
An attribute that can have only one value.
single-valued attribute
A relationship that occurs when two entities are existence-dependent.
From a database design perspective, this relationship exists whenever the primary key of the related entitity contains the primary key of the parent entity.
strong (identifying) relationship
An ER term used to describe an association (relationship) between three entities.
For example, a DOCTOR prescribes a DRUG for a PATIENT
ternary relationship
An ER term used to describe an association within an entity.
For example, an EMPLOYEE might manage another EMPLOYEE.
unary (recursive) relationship
An entity that displays existence dependence and inherits the primary key of its parent entity.
For example, a DEPENDENT requires the existence of an EMPLOYEE.
weak entity
A relationship in which the primary key of the related entity does not contain a primary key component of the parent entity.
weak (non-identifying) relationship
