Relational Database Model
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Relational Database Model - Database Management and Design - Lecture Slides, Slides of Introduction to Database Management Systems
Some concept of Database Management and Design are Advanced SQL, Database Design, Database Administration, Databases In Electronic Commerce, Entity Relationship Modeling, Intro To Database Systems. Main points of this lecture are: Relational Database Model, Database, Logical View, Relational, Components, Relationships Among, Entities, Attributes, Organized, Database Operators
Typology: Slides
2012/2013
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Relational Database Model
In this chapter, you will learn:
- That the relational database model takes a logical view of data
- That the relational model’s basic components are entities, attributes, and relationships among entities
- How entities and their attributes are organized into tables
A Logical View of Data
- Relational model
- Enables us to view data logically rather than physically
- Reminds us of simpler file concept of data storage
- Table
- Has advantages of structural and data independence
- Resembles a file from conceptual point of view
- Easier to understand than its hierarchical and network database predecessors
Tables and Their
Characteristics
- Table : two-dimensional structure composed of rows and columns
- Contains group of related entities an entity set - Terms entity set and table are often used interchangeably
Characteristics of a Relational Table
Table 3.
STUDENT Table Attribute Values
Student Classification
Keys (continued)
- Composite key
- Composed of more than one attribute
- Key attribute
- Any attribute that is part of a key
- Superkey
- Any key that uniquely identifies each entity
- Candidate key
- A superkey without redundancies
Controlled Redundancy
- Makes the relational database work
- Tables within the database share common attributes that enable us to link tables together
- Multiple occurrences of values in a table are not redundant when they are required to make the relationship work
- Redundancy is unnecessary duplication of data Docsity.com
An Example of a
Simple Relational Database
Keys (continued)
- Foreign key (FK)
- An attribute whose values match primary key values in the related table
- Referential integrity
- FK contains a value that refers to an existing valid tuple (row) in another relation
- Secondary key
- Key used strictly for data retrieval purposes