The document outlines key concepts related to data models and relational databases, including definitions of terms such as relation, attribute, tuple, and schemas. It explains the properties of relations and the importance of relational keys, emphasizing concepts like primary and foreign keys. Additionally, it addresses relational integrity and constraints, highlighting the necessity for data correctness within a database.

1. Data Model

2. Data Models
 A collection of conceptual tools for
describing
 data
 data relationships
 data semantics
 data constraints
 Relational model
 Entity-Relationship model
 Other models:
 object-oriented model
 semi-structured data models
 Older models: network model and hierarchical model

3. Relational Data Structure
 RelationRelation
 A table with columns and rows
 AttributeAttribute
 Named column of a relation
 DomainDomain
 Set of allowable values for one or more attributes
 TupleTuple
 A row in a relation
 DegreeDegree (of a relation)
 The number of attributes it contains
 CardinalityCardinality (of a relation)
 The number of tuples it contains
3

4. Alternate Terminology
4
Formal Terms Alternative 1 Alternative 2
Relation Table File
Tuple Row Record
Attribute Column Field

5. Mathematical Relations
D1 = {2, 4} and D2 = {1, 3, 5}
D1xD2 = {(2,1), (2,3), (2,5), (4,1), (4,3), (4,5)}
• Any subset of this Cartesian Product is a Relation
5

6. Database Relations
 Relation SchemaRelation Schema
 A named relation defined by a set of attributes and
domain name pairs
 Relational Database SchemaRelational Database Schema
 A set of relation schemas each with a distinct name
6

7. Properties of Relations
 Has a name that is different from all other
relation names
 Each cell of a relation contains exactly one
atomic value (no arrays)
 Each attribute has a distinct name
 The values of an attribute are all from the same
domain
 Each tuple is distinct (no duplicate rows)
 The order of attributes has no significance
7

8. Relational Keys
 SuperkeySuperkey
 An attribute or a set of attributes that uniquely identifies a tuple
 Candidate KeyCandidate Key
 A superkey such that no proper subset is a superkey
 Primary KeyPrimary Key
 The candidate key that is selected to identify the tuples uniquely
 Foreign KeyForeign Key
 An attribute or a set of attributes within one relation that
matches the candidate key of some relation
8

9. Representing Relational
Database Schemas
Branch(branchNo, street, city, postCode)
Staff(staffNo, fName, lName, position, gender, DOB,
salary, branchNo)
PropertyForRent(propertyNo, street, city, postCode,
type, rooms, rent, ownerNo, staffNo, branchNo)
…
9

10. Relational Integrity
• Constraints placed on database in order to ensure
that the data is correct.
• For example, domain constraints, entity integrity
rules, referential integrity rules and other rules
(enterprise constraints)
10

11. Relational Integrity
 Entity IntegrityEntity Integrity
 In a relation no attribute of a primary key can be null.
 Referential IntegrityReferential 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/parent relation or the foreign key
must be wholly null.
11