02_04 ER Modeling

Question 1

An ER term for an association (relationship) between TWO entities.

For example, PROFESSOR teaches CLASS.

Answer 1

binary relationship

Question 2

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.

Answer 2

cardinality

Question 3

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).

Answer 3

composite attribute

Compare to simple attribute

Question 4

In ER modeling, a key composed of more than one attribute.

Answer 4

composite identifier

Question 5

The type of relationship between entities.

Answer 5

connectivity

Question 6

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.

Answer 6

derived attribute

Question 7

A property of an entity whose existence depends on one or more other entities.

Answer 7

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.

Question 8

A property of an entity that can exist apart from one or more related entities.

Answer 8

existence-independent

Such a table must be created first when referencing an existence-dependent table.

Question 9

One or more attributes that uniquely identify each entity instance.

Answer 9

identifier

Question 10

A process based on repetition of steps and procedures.

Answer 10

iterative process

Question 11

A relationship in which one entity must have a corresponding occurrence in another entity.

Answer 11

mandatory participation

Question 12

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.

Answer 12

multivalued attribute

Question 13

In ER modeling, a condition in which one entity occurrence does not require a corresponding entity occurrence in a particular relationship.

Answer 13

optional participation

Question 14

In ER modeling, an attribute that does not require a value.

It can be left empty.

Answer 14

optional attribute

Question 15

An ER term for entities that participate in a relationship.

Answer 15

participants

For example, in the relationship “PROFESSOR teaches CLASS,” the teaches relationship is basedo nthe participants PROFESSOR and CLASS.

Question 16

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.

Answer 16

recursive(unary) relationship

Question 17

An entity that is existence-independent.

Answer 17

strong entity (regular entity)

Question 18

The organization of a relational database as described by the database administrator.

Answer 18

relational schema

Question 19

The number of entities or participants associated with a relationship.

Can be unary, binary, ternary, or higher.

Answer 19

relationship degree

Question 20

In ER modeling, an attribute that must have a value.

It cannot be left empty.

Answer 20

required attribute

Question 21

An attribute that cannot be subdivided into meaningful components.

Answer 21

simple (atomic) attribute

Compare to composite attribute

Question 22

An attribute that can have only one value.

Answer 22

single-valued attribute

Question 23

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.

Answer 23

strong (identifying) relationship

Question 24

An ER term used to describe an association (relationship) between three entities.

For example, a DOCTOR prescribes a DRUG for a PATIENT

Answer 24

ternary relationship

Question 25

An ER term used to describe an association within an entity.

For example, an EMPLOYEE might manage another EMPLOYEE.

Answer 25

unary (recursive) relationship

Question 26

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.

Answer 26

weak entity

Question 27

A relationship in which the primary key of the related entity does not contain a primary key component of the parent entity.

Answer 27

weak (non-identifying) relationship