DATABASES

Entity-Relationship Model (ERD)

It represents the conceptual database as viewed by the end user.

Single-valued attribute

An attribute that can have only a single value.

Multivalued attribute?

An attribute that can have many values.

Derived attribute?

An attribute whose value is calculated from other attributes.

Required attribute?

An attribute that must have a value.

optional attribute.

An attribute that does not require a value.

Domain

A set of possible values for a given attribute.

Identifier (PK)

One or more attributes that uniquely identify each entity instance.

Composite Identifier

A primary key composed of more than one attribute.

composite attribute.

An attribute that can be further subdivided to yield additional attributes.

simple attribute?

An attribute that cannot be subdivided.

participants

Entities that participate in a relationship.

connectivity

It is used to describe the relationship classification.

cardinality

The minimum and maximum number of entity occurrences associated with one occurrence of the related entity.

existence dependence

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

existence independence.

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

strong entity

An entity that is existence-independent and can exist apart from all of its related entities.

weak entity

Displays existence dependence and inherits the primary key from another entity.

weak relationship

A relationship that does not contain a primary key component of the parent entity.

strong relationship.

Exists when the primary key of the related entity contains a primary key component.

optional attribute

One entity occurrence does not require a corresponding entity occurrence in a relationship.

mandatory participation

One entity occurrence requires a corresponding entity occurrence in a relationship.

unary relationship

Describes association within the same entity.

binary relationship

Exists when two entities are associated.

ternary relationship

Exists when three entities are associated.

recursive relationship

A relationship that exists between occurrences of the same entity.

relationship degree indicate

The number of entities or participants associated with a relationship.

relational schema

The organization of a relational database.

iterative process.

A process based on repetition of steps and procedures.

What is an Entity-Relationship Diagram (ERD)?

It represents the conceptual database as viewed by the end user.