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existence-independent -answer-A property of an entity that can exist apart from one or
more related entities. Such a table must be created first when referencing an existence-
dependent table.
identifiers -answer-One or more attributes that uniquely identify each entity instance.
iterative process -answer-A process based on repetition of steps and procedures.
mandatory participation -answer-A relationship in which one entity occurrence must
have a corresponding occurrence in another entity. For example, an EMPLOYEE works
in a DIVISION. (A person cannot be an employee without being assigned to a
company's division.)
multivalued attributes -answer-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.
non-identifying relationship -answer-A relationship in which the primary key of the
related entity does not contain a primary key component of the parent entity.
optional attribute -answer-In ER modeling, an attribute that does not require a value;
therefore, it can be left empty.
, optional participation -answer-In ER modeling, a condition in which one entity
occurrence does not require a corresponding entity occurrence in a particular
relationship.
participants -answer-An ER term for entities that participate in a relationship. For
example, in the relationship "PROFESSOR teaches CLASS," the teaches relationship is
based on the participants PROFESSOR and CLASS.
recursive relationship -answer-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.
relational schema -answer-The organization of a relational database as described by
the database administrator.
relationship degree -answer-The number of entities or participants associated with a
relationship. A relationship degree can be unary, binary, ternary, or higher.
required attribute -answer-In ER modeling, an attribute that must have a value. In other
words, it cannot be left empty.
simple attribute -answer-An attribute that cannot be subdivided into meaningful
components. Compare to composite attribute.
single-valued attribute -answer-An attribute that can have only one value.
strong (identifying) relationship -answer-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 entity contains the primary key of the parent
entity.
strong entity -answer-An entity that is existence-independent, that is, it can exist apart
from all of its related entities. Also called a regular entity.
ternary relationship -answer-An ER term used to describe an association (relationship)
between three entities. For example, a DOCTOR prescribes a DRUG for a PATIENT.
unary relationship -answer-An ER term used to describe an association within an
entity. For example, an EMPLOYEE might manage another EMPLOYEE.
weak entity -answer-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 relationship -answer-A relationship in which the primary key of the related entity
does not contain a primary key component of the parent entity.