Download Database Systems: Design, Implementation, and Management

Chapter 6
Database
Design
Database Systems: Design,
Implementation, and Management
CHAPTER 6
Database Design
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
1
Chapter 6
Database
Design
The Systems Development Life Cycle
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The Systems Development Life Cycle (SDLC)
provides a methodology for developing an IS.
Database design takes place within the confines of
an IS.
Five phases of SDLC:
 Planning
 Analysis
 Design
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
 Implementation
 Maintenance

SDLC is an iterative process
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SDLC
Chapter 6
Database
Design
Planning
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
• Enterprise-wide requirement assessment
• Identification of IS projects
• Feasibility assessment and prioritization
Analysis
• User requirement analysis for a specific project
• Requirement modeling (conceptual)
Design
• Detailed design
• Specification development
Implementation
Maintenance
• Coding, testing and evaluation
• Installation
• Daily operation and maintenance
• Enhancements
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Chapter 6
Database
Design
Database Life Cycle
Database Initial
study
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
• Analyze company situation
• Define problem
• Define objectives
• Define scope and boundaries
Database Design
• Conceptual design
• DBMS software selection, if required
• Logical design
• Physical design
Implementation
and loading
• Install DBMS, if new
• Create databases
• Load data
Testing and
evaluation
Operation and
maintenance
• Test the database
• Evaluate performance and fine-tune
• Daily operation and maintenance
• Enhancements
This is also an iterative process like SDLC
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Database Design
Chapter 6
Database
Design

Divided into four tasks
 Conceptual
design
 DBMS software selection (if required)
 Logical design
 Physical design
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Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel

Conceptual design is independent of software and
hardware
Logical design is DBMS (software) dependent
Physical design is dependent on both software and
hardware
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Conceptual Design
Chapter 6
Database
Design
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The goal is to capture and model user requirements
Four Steps:
 Data
analysis and requirements
 Entity relationship modeling and normalization
 Data model verification
 Distributed database design
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
6
Conceptual Design
Chapter 6
Database
Design

Data analysis and requirements
 The
focus is on identifying user requirements
 This can be gathered through various mean

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observing and analyzing the current system
user interviews
questionnaire surveys
 Capture
and document user data views and business
rules.

Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
User data views describe the data used by the user


Example
Business rules describe policies and procedures followed by
the company

Example: (EZS)
 An item may be procured from many vendors
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 Purchase price of an item is negotiated with each supplier.
Conceptual Design
Chapter 6
Database
Design

ER Modeling and Normalization
 User
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

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
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel

requirements are modeled using E-R diagrams
Identify main entities based on user requirements data
Define relationships between the entities
Define attributes, primary keys, and foreign keys for each
of the entities.
Normalize the entities.
Complete the initial E-R diagram.
Verify the E-R model against the data, information, and
processing requirements.
Modify the E-R diagram, if necessary
 Documentation
process must be standardized to
avoid miscommunication
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Conceptual Design
Chapter 6
Database
Design

Data model verification
 Ensure
that user data views can be supported by the
data model
 All business transactions (select, insert, update,
delete, user queries) can be supported by the model

Distributed database design
 Data
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
requirements and processing requirements may
vary from one location to another
 Decision may be made about allocating data to
different locations
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DBMS Selection
Chapter 6
Database
Design
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
This step is required only if you plan to acquire a
new DBMS
Common factors affecting the decision:
 Cost
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
-- Purchase, maintenance, operational, license,
installation, training, and conversion costs.
 DBMS features and tools.
 Underlying model.
 Portability -- Platforms, systems, and languages.
 DBMS hardware requirements.
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Logical Design
Chapter 6
Database
Design
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Logical design translates the conceptual design into
the internal model for a selected DBMS.
It includes the design of tables, indexes, views,
transactions
Access authorities (who can access what) are also
decided.
The ER model is translated into relational schema
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
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Logical Design
Chapter 6
Database
Design

Translating ER Model into Relational Schema
 After
normalizing the E-R diagram we are left with
only two types of relationships
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One-to-one
One-to-Many
 For
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
every one-to-one relationship, reexamine the
possibility of merging the two entities into a single
entity by combining their attributes.
 Entities participating in a one-to-one relationship are
linked through a foreign key.
 Supertype-subtype relationships are usually
implemented as one-to-one relationships. Both
entities share a common primary key, which also
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becomes a foreign key in the subtype entity.
Logical Design
Chapter 6
Database
Design
1
Employee
1
(0,1)
(1,1)
Employee
Driver
1
Emp_Id
Emp_Name
Emp_Salary
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
Driver
May be a
Primary and Foreign
Key
1
Emp_Id
License Nbr
Lic Exprn. Date
Example of translating a 1:1 relationship into a relational schema
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Logical Design
Chapter 6
Database
Design

Translating ER Model into Relational Schema
 One-to-many
relationships are implemented by
adding the primary key of the first entity as the
foreign key of the second (many side) entity.
Example:
1
M
Professor
Class
teaches
(0,N)
(1,1)
Professor
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
Class
1
Prof_Id
Prof_Lname
Prof_Phone
M
Class_Code
Class_Section
Class_Days
Class_Time
Prof_Id
Foreign Key
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Example - Logical Design
Chapter 6
Database
Design
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
PROF_ID
Is a valid professor identification number.
Type: numeric
Range: low value = 1,000
high value =2,000
Display format: 9999
Length: 4
PROF_LNAME
Is a valid professor last name.
Type: character
Display format: XXXXXXXXXXXXXXX
Length: 15
PROF_PHONE
Is a valid phone number.
Type: character
Display format: 999-999-9999
Length: 12
CLASS_CODE
Is a valid class code.
Type: numeric
Range: low value = 1,000
Display format: 9999
Length: 4
high value =1,999
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Chapter 6
Database
Design
Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel
Example - Logical Design
CLASS_SECTION
Is a valid is a valid class section number.
Type: numeric
Range: low value = 10
high value = 99
Display format: 99
Length: 2
CLASS_DAYS
Is a valid day code.
Type: character
Valid entries: MWF, TTh, M, T, W, Th, F
Display format: XXX
Length: 3
CLASS_TIME
Is a valid time.
Type: character
Display format: 99:99 (24-hour clock)
Display range: 00:01 to 24:00
Length: 5
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Physical Design
Chapter 6
Database
Design
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Database
Systems:
Design,
Implementation,
And
Management
Peter Rob &
Carlos Coronel

Select data storage and data access characteristics
(indexes) of the database.
It affects location of the data in the storage
device(s) and system performance.
Physical design is more complex with distributed
databases.
Relational databases are more insulated from
physical layer details than hierarchical and network
models.
Chapters 7 and 8 describe an excellent case
study of database design
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