Iman

Entities

In the ERM, it corresponds to a table—not to a row.

Required Attributes

In ER modeling, an attribute that must have a value; it cannot be left empty.

Optional Attributes

An attribute that does not require a value; therefore, it can be left empty.

Domains

The possible set of values for a given attribute.

Identifiers

One or more attributes that uniquely identify each entity instance.

Relational Schema

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

Composite Identifiers

A 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 into meaningful components.

Single-Valued Attributes

An attribute that can have only one value.

Multivalued Attributes

An attribute that can have many values for a single entity occurrence.

Derived Attributes

An attribute that does not physically exist within the entity and is derived via an algorithm.

Relationship

An association between entities.

Participants

The entities that participate in a relationship.

Connectivity

The term used to describe the relationship classification.

Cardinality

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.

Existence-dependent

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

Existence-independent

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

Strong Entity (Regular Entity)

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

Weak (Non-Identifying) Relationships

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

Strong (Identifying) Relationships

A relationship that occurs when two entities are existence dependent.

Participation in an entity relationship

Is either optional or mandatory.

True/False

Relationships aren't bidirectional.

Relationship Degree

Indicates the number of entities or participants associated with a relationship.

Unary Relationship

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

Binary Relationship

An ER term for an association between two entities.

Ternary Relationship

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

Recursive Relationship

A relationship found within a single entity type.

Associative Composite Entities

M:N relationships are a valid construct found frequently during the ER modeling process.

Associative Entity

The ER Model uses this to represent an M:N relationship between two or more entities.

Associative Composite Entities

Also called a composite or bridge entity.

Conflicting Goals

Database designers must often make design compromises that are triggered by factors like design standards, processing speed, and information requirements.

Design Standards

Standards that guide you in developing logical structures that minimize data redundancies.

Processing Speed

High processing speed means minimal access time.

Information Requirements

Complex requirements may dictate data transformations and expand the number of entities and attributes within the design.

SQL Functions

Named, reusable sequences of SQL statements that perform specific operations based on arguments.

Relational Set Operations

Set of functions that allow you to combine results from multiple SELECT statements.