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CS3754 Class Note 12
Summery of Relational Database
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Database Technology
• A collection of related data organized in
a way that makes it valuable and useful
• Allows organizations to retrieve, store,
and analyze information easily
• Is vital to an organization’s success in
running operations and making
decisions
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Database Terminology
Entities
• Things we store information about. (i.e.
persons, places, objects, events, etc.)
• Have relationships to other entities (i.e. the
entity Student has a relationship to the entity
Grades in a University Student database
Attributes
• These are pieces of information about an
entity (i.e. Student ID, Name, etc. for the
entity Student)
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File Processing vs Database Approach Summary
File Processing Approach (Old School)
• Storage Media: Sequential tapes or files
• Data: stored in long sequential files
• Organization: redundant data in multiple files
• Efficiency: data embedded to support processing
• Updates: requires multiple updates in many files
• Processing: slower query/faster processing
Data Base Approach (New School-TODAY)
• Storage Media: Direct Access Storage Device (DASD)
• Data: stored in related tables
• Organization: redundant data minimized/eliminated
• Efficiency: data only stored only in tables
• Updates: requires few or one update for a data field
• Processing: faster query/slower processing
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Advantages of the Database Approach
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Roles in Database Development and Use
Database Administrator (DBA)
• Designs, develops and monitors
performance of databases
• Enforces policy and standards
for data uses and security
Systems Programmer
• Creates business applications
that connect to databases
• Tests the new systems and
databases before use
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Systems Analyst
• Defines data requirements
working with a DBA
• Incorporates the database
design into new program
designs
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Designing Databases – Data Model
ER or EER Data Model (Conceptual Data Model)
• A map or diagram that represents entities and
their relationships
• Used by Database Administrators to design tables
with their corresponding associations
Example: ERD (Entity Relationship Diagram)
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Designing Databases – Keys
Database Keys
Mechanisms used to identify, select, and maintain one or
more records using an application program, query, or report
Primary Key
A unique attribute type used to identify
a single instance of an entity.
Compound Primary Key
A unique combination of attributes types used to
identify a single instance of an entity
Secondary Key
An attribute that can be used to identify one or more records
within a table with a given value
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Designing Databases – Keys (Example)
Primary
Key
ENTITIES
- Student ID
Entities are translated
into Tables
(Students and Grades)
Secondary
Key
- Major
Entities are
joined by
common
attributes
Compound
Primary Key
- Student ID
- Course ID
- Sec No.
- Term
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Designing Databases - Associations
Associations
• Define the relationships one entity has to another
• Determine necessary key structures to access data
• Come in three relationship types:
- One-to-One
- One-to-Many
- Many-to-Many
Foreign Key
• An attribute that appears as a non-primary
key in one entity (table) and as a primary key
attribute in another entity (table)
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Designing Databases - Associations
Entity Relationship Diagram (ERD)
• Diagramming tool used to express entity relationships
• Very useful in developing complex databases
Example
• Each Home Stadium has a Team (One-to-One)
• Each Team has Players (One-to-Many)
• Each Team Participates in Games
• For each Player and Game there are Game Statistics
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Designing Databases - Associations
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Designing Databases – Associations (Example)
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The Relational Model
The Relational Model
• The most common type of database model used
today in organizations
• Is a three-dimensional model compared to the
traditional two-dimensional database models
- Rows (first-dimension)
- Columns (second-dimension)
- Relationships (third-dimension)
• The third-dimension makes this model so powerful
because any row of data can be related to any
other row or rows of data
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The Relational Model - Example
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The Relational Model - Normalization
Normalization
• A technique to make complex databases more efficient by
eliminating as much redundant data as possible
• Example: Database with redundant data (below)
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The Relational Model - Normalization
Normalized Database
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The Relational Model – Data Dictionary
Data Dictionary
• Is a document that database designers prepare to help
individuals enter data
• Provides several pieces of information about each
attribute in the database including:
- Name
- Key (is it a key or part of a key)
- Data Type (date, alpha-numeric, numeric, etc.)
- Valid Value (the format or numbers allowed)
• Can be used to enforce Business Rules which are
captured by the database designer to prevent illegal or
illogical values from entering the database. (e.g. who has
authority to enter certain kinds of data)
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Organizational Use of Databases
Operational
Informational
Extract
Data
Extract
Data
Department
Databases
Data
Warehouse
• Day to Day
Department
Transactions
• Used primarily by
departments
• Extracted
Department
transactions
• Used for
business
analysis
Information Systems Today
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Data
Mart
• Extracted
subset of a data
warehouse
• Used for highly
specific business
analysis
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Data Mining
Data Mining
• Is a method companies use to analyze information to
better understand their customers, products, markets, or
any other phase of their business for which they have
data
• With data mining tools you can graphically drill down,
sort or extract data based on certain conditions,
perform a variety of statistical analysis
• Data mining applications are very powerful and use highly
complex algorithms to analyze and to identify
opportunities
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Data Warehouse Example
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Uses of Data Warehousing
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