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Chapter 5
Database Processing
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What Is the Purpose of a Database?
•
Organize and keep track of things
•
Keep track of multiple themes
•
General rule:
 Single theme store in a spreadsheet
 Multiple themes require a database
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A List of Student Grades Presented in a
Spreadsheet – Single Theme
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Data Redundancy and Data Inconsistency
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Student Data Form With Multiple
Themes
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Why we need databases
• Size
• Ease of Updating
• Accuracy
• Security
• Redundancy
• Importance
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Components of a Database
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Tables
Table or file:
A group of records
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Tables (cont’d)
Each table must
have a unique
identifier called the
Primary Key (PK)
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More Special Terms
Relational
databases
Relation
•Relationships among tables are
created by using foreign keys
•Formal term for a table
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Relationships Among Records
Database has multiple tables (one
for each theme)
Values in one table may relate to
records in other tables
Relational
database
Primary or
Unique key
Foreign key
Field(s) that uniquely
identify a record in a table
Each table must have a key
A non-primary key in one table
that is related to a primary key
of a different table
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Primary and Foreign Keys
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Metadata
Database: Self-describing collection of integrated records
Metadata
Describes data by:
•Data that describes data
•Makes databases more
useful
•Makes databases easier
to use
•Data type: text, number,
date, etc.
•Field name
•Field properties
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Sample Metadata in Access
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Features of Relational Databases
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Features of Relational Databases
(cont’d)
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What Is a DBMS and What Does It Do?
Database management system (DBMS)
― Program that creates, processes, and administers
databases
― Examples:
Database
Collection of
tables,
relationships,
and
metadata
DBMS
A
software
program
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Components of a Database Application
System
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Processing the Database
Four DBMS operations
1. Read
2. Insert
3. Modify
4. Delete data
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Structured Query Language (SQL)
•
SQL (see-quell)
• International standard
• Used by most popular DBMS
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Structured Query Language (SQL)
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Database Applications
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Forms, Reports, and Queries
Forms
• Used to read, insert, modify,
and delete data
Reports
• Show data in structured
context
• May compute values such as
Totals, within a report
Queries
• Are a means of getting
answers from database data
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How Are Database Application Systems Developed?
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How Are Database Application Systems Developed?
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What Are the Components of the
Entity-Relationship Data (ERD) Model?
Entities
• Something users want to track
• Order, customer, salesperson, item,
volunteer, donation
Attributes
• Describe characteristics of an entity
• OrderNumber, CustomerNumber,
VolunteerName, PhoneNumber
Identifier
• Attribute that uniquely identifies one
entity instance from other instances
• Student_ID_Number
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Creating ERDs
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Student Data Model Entities
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Example of Department, Adviser, and
Student Entities and Relationships
A
department
may have
many
advisers
An adviser
works in one
department
1:N relationships
An adviser
advises
many
students
A student
may have
one or more
advisers
N:M relationships
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Example of Department, Adviser, and
Student Entities and Relationships
N:M
1:N
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Entity Relationship Diagram (ERD) ― Version 1
Crow’s
Feet
1:N
1:N = one-to-many relationships
One department can have many
advisers, but an adviser is in
only one department
N:M
N:M = many-to-many
relationships
One adviser can have many
students and one student
can have many advisers
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Entity Relationship Diagram (ERD) – Version 2
“Crow’s Foot”
N:M = many-to-many
relationship
1:N = one-to-many
relationship
A department has many
advisors and an advisor
may advise for more
than one department
A student has only one
advisor, but an adviser
may advise many
students
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Defining one-to-many relationships
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How Are Database Application Systems Developed?
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Transforming a Data Model into a Database
Design
• Represent each entity with a table
‒ Entity identifier becomes table key
‒ Entity attributes become table columns
• Normalize tables as necessary
• Represent relationships
‒ Use foreign keys
‒ Create additional tables for N:M relationships
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Representing 1:N Relationships
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Exploring many-to-many relationships
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Representing an N:M Relationship: Strategy
for Foreign Keys
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How Are Database Application Systems Developed?
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What Is the Difference Between an
Enterprise DBMS and a Personal DBMS?
Enterprise DBMS
Personal DBMS
• Processes large
organizational and
workgroup databases
• Supports many users
(thousands plus)
• Examples: DB2, SQL Server,
Oracle, MySQL
• Designed for smaller,
simpler database
applications
• Supports fewer than 100
users (mostly 1–10 users)
• Examples: Access, dBase,
FoxPro, R-Base
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