1. Thomas Connolly and Carolyn Begg’s
Database Systems:
A Practical Approach to Design, Implementation, and Management
Chapter 4 Part One:
Relational Terminology
Of course, we are still using Kroenke’s slide format!

2. Today’s Objectives
To understand the terminology of the relational model.
Properties of database relations
The meaning of entity integrity and referential integrity

3. The Relational Database Model
The dominant database model is the relational database model – all current major DBMS products are based on it
Created by IBM engineer E. F. Codd in 1970
It was based on mathematics called relational algebra
DAVID M. KROENKE’S DATABASE PROCESSING, 10th Edition
© 2006 Pearson Prentice Hall

4. The Relational Model
“The Relational Database Management System(RDBMS) has become the dominant data-processing software in use today, with estimated sales of between US$15 billion and US$20 billion per year,…, and growing at a rate of possibly 25% per year.” Connolly, Begg. P. 70
A relation is viewed as a two dimensional table of data where columns are the attributes of the data and rows, or tuples, contain records of the user data.
Each row contains one piece of data per column.

5. Database Relations
Relation schema: A named relation defined by a set of attribute and domain pairs. [p.76]
Relational database schema: A set of relation schemas, each with a distinct name. [p. 76]

6. Properties of Relations
The relation has a name that is distinct from all other relation names in the relation schema
Each cell of the relation contains exactly one single value
Each attribute has a distinct name
The values of an attribute are all from the same domain
Each tuple is distinct
The order of attributes has no significance
The order of tuples has no significance
[p.77]

7. Relational Keys
Superkey: An attribute, or set of attributes, that uniquely identifies a tuple within a relation.
Candidate key: A superkey such that no proper subset is a superkey within the relation.
Primary key: The candidate key that is selected to identify tuples uniquely within the relation.
Foreign key: An attribute, or set of attributes, within one relation that matches the candidate key of some (possibly the same) relation.
[p.80]

8. Relational Integrity
Domain constraints form restrictions on the set of values allowed for the attributes of relations.
Null: Represents a value for an attribute that is currently unknown or is not applicable for this tuple.
Entity Integrity: No attribute of the primary key can be null.
Referential Integrity: If a foreign key exists in a relation, either the foreign key value must match a candidate key value of some tuple in its home relation or the foreign key value must be wholly null.
[pp ]

9. Of course, we are still using Kroenke’s slide format!
Thomas Connolly and Carolyn Begg’s Database Systems: A Practical Approach to Design, Implementation, and Management
End of Presentation
Of course, we are still using Kroenke’s slide format!