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Database Management System
Lecture 4
The Relational Database ModelIntroduction, Relational Database
Concepts
Introduction
• In this lesson, an introduction to the relational
database model is provided.
• Description of the main building blocks of a
relational database and its definition.
Learning Outcomes
• Understand how a relation (table) is the main
organization unit of a database.
• Understand the main building blocks of a
relational database and its definition
Terminology
• Domain A set of values that define the value
range for an attribute.
• Attribute The basic unit in a relation (table)
definition. Each attribute has a domain
associated with it.
Terminology (Cont.)
• Relation Schema (Table Schema) Defines the
structure of a relation (table) which consists of
a set of attributes and an association between
each attribute and its domain
• Relational Database Schema A collection of
relation (table) schemas
Terminology (Cont.)
• Tuple (record/row) A list of values with each
value being an element in a domain or NULL.
A tuple represent a record or row in a table
(relation).
• Relation (Table) An instance of a relation
schema which is composed of a set of tuples
Terminology (Cont.)
• Database A collection of relations (tables).
Introduction to the Relational
Database Model
• As discussed in the previous lecture, the
relational database model is the most widely
used data model in DBMSs.
• It was developed by E. F. Codd at IBM in
1970.
Introduction to the Relational
Database Model (Cont.)
• The relational database model is based on
organizing data with the basic organization
unit being a relation that is represented as a
table.
Relational Database Concepts
Domain:
• is a set of values that define the value range for
an attribute.
• A domain can be considered as a data type.
Examples of domains include integer, float,
string, date, etc.
Relational Database Concepts (Cont.)
• Relation Schema (Table Schema): defines
the structure of a relation (table) which
consists of a set of attributes and an
association between each attribute and its
domain (specifying the possible values of an
attribute).
• Relational Database Schema: that is a
collection of relation (table) schemas.
Relational Database Concepts (Cont.)
Attribute:
• is the basic unit in a relation (table) definition.
• Each attribute has a domain associated with it.
It can be considered as a column in relational
database table.
Relational Database Concepts (Cont.)
• Tuple (Record/row):
• that is a list of values with each value being an
element in a domain or NULL.
• A tuple represent a record or row in a table
(relation).
Relational Database Concepts (Cont.)
Relation (Table):
• is one instance of a relation schema which is
composed of a set of tuples.
Relational Database:
• is a collection of relations (tables).
• Figure 5.1 illustrates the definition of Library
database.
• A database schema is defined which consists of
two relation (table) schemas: Books and
Members.
• As shown in the books table schema in Figure
5.1, the schema defines the structure of the
table specifying the attributes of the table
(book_Id, title, author, publisher and
publication_date).
• Each attribute is associated with a domain in
the schema, e.g. attribute title has domain text
which specifies that values of attribute title are
of type text.
• Figure 5.2 illustrates the library database
instance.
• It can be seen that the library database
consists of two relations (tables): books and
members.
• The books table is an instance of the books
table schema shown in Figure 5.1.
• The books table
(records/rows).
consists
of
tuples
• Each tuple is composed of values for the
attributes defined in the table schema.
• Each value in a table tuple is part of the
domain associated with the corresponding
attribute in the table schema.
• For example, value ‘A Tale of Two Cities’ in
the 1st tuple of the book table is a value of
attribute title with domain text as defined in
the table schema (shown in Figure 5.1).
Summary
• An Introduction to the Relational Database
Model
• The main relational database concepts.