15.00 - Definition of a Relationship - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Definition of a Relationship

A relationship is an association among two or more entities or other relationships. Relationships are expressed as verbs.

Relationships among entities are described by one of three ratios:

 

Relationship

Shorthand Notation

One-to-one

1:1

One-to-many

1:M

Many-to-many

M:M

Relationships as defined in the E-R model have no direct counterpart in relational theory. The closest property of relational theory to expressing what a relationship is in E-R theory is the primary key-foreign key relationship.

“Relationship Theory” on page 67, “One-to-One Relationships” on page 68, “One-to-Many Relationships” on page 69, and “Many-to-Many Relationships” on page 70 describe the properties of relationships in greater detail.