Database Systems – Chapter 4 Glossary terms

binary
relationship
An ER term for an association (relationship) between two entities. For example, PROFESSOR
teaches COURSE.
cardinality
A property that assigns a specific value to connectivity and expresses the range of allowed entity
occurrences associated with am single occurrence of the related entity
composite
attribute
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), an exchange number (898),
and a four-digit code (2368). Compare to simple attribute.
composite
identifier
In ER modeling, a key composed of more than one attribute.
connectivity
The classification of the relationship between entities. Classifications include 1:1, 1:M, and M:N.
derived
attribute
An attribute that does not physically exist within the entity and is derived via an algorithm. For
example, the Age attribute might be derived by subtracting the birth date from the current date.
existence-dependent
A property of an entity whose existence depends on one or more other entities. 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.
existence-independent
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
In an ERM, unique names of each entity instance. In the relational model, such identifiers are
mapped to primary keys in tables.
identifying
relationship
A relationship in which related entities are existence-dependent. Also called a strong
relationship or strong identifying relationship because the dependent entity’s primary key contains
the primary key of the parent entity
iterative
process
A process based on repetition of steps and procedures.
mandatory
participation
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
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
A relationship in which the primary key of the dependent (many side) entity does not contain the primary key of the related parent entity. Also known as a weak relationship.
optional
attribute
In ER modeling, an attribute that does not require a value; therefore, it can be left empty.
optional
participation
In ER modeling, a condition in which one entity occurrence does not require a corresponding entity
occurrence in a particular relationship.
participants
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
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
The organization of a relational database as described by the database administrator.
relationship
degree
The number of entities or participants associated with a relationship. A relationship degree can be
unary, binary, ternary, or higher.
required
attribute
In ER modeling, an attribute that must have a value. In other words, it cannot be left empty
simple
attribute
An attribute that cannot be subdivided into meaningful components. Compare to composite
attribute.
single-valued
attribute
An attribute that can have only one value.
strong
(identifying)
relationship
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.
ternary
relationship
An ER term used to describe an association (relationship) between three entities. For example, a
CONTRIBUTOR contributes money to a FUND from which a RECIPIENT receives money.
unary
relationship
An ER term used to describe an association within an entity. For example, a COURSE might be a
prerequisite to another COURSE.
weak entity
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
A relationship in which the primary key of the related entity does not contain a primary key
component of the parent entity. Also known as a non-identifying relationship.