What is a relational model

Business Intelligence (Part 3): Data Modeling - Relational and Multidimensional Models

Relational data models

The best known and “most modern” data model is the relational one. It's simple and easy to understand, and more geared towards user needs. It also allows a better implementation of data independence.

The relational database model was first proposed in 1970 by Edgar Codd - today it is an established standard for storing data. The associated database management system (DBMS) is referred to as a relational database management system (RDBMS). The Structured Query Language (SQL) is used as the data manipulation language for querying and manipulating the data.

Relational data models are based on relations with a name and associated attributes. The relations are shown in the form of two-dimensional tables with clear names. Each record is a row (tuple) in the table. The lines can be clearly identified using one or more primary keys. The attribute values ​​form the columns of the table.

The relation scheme defines the number and type of attributes for a relation. The figure illustrates the relationship R. with the attributes A1 to At in the columns and the values ​​arranged in rows.

Entity relationship models can easily be converted into relational models. Each entity type and each complex relationship type (n: m relationship) in the relationship model becomes its own relationship. The following table compares the terms from both models.

Relational data model

Entity Relationship Model (ERM)

Range of values ​​(domain, domain)

Range of values ​​(domain, domain)

Range of values ​​(domain, domain)

Header

Relation type / relation format

Entity type

Column heading

attribute

attribute

content

relation

Entity set (-set)

content

Foreign key

Relationship

row

Tuple

entity

cell

Attribute value

Attribute value