1. Database Management Systems ISYS 464
David Chao

2. Introduction to Databases
The most important component in an information system
Created to support all levels of business operations:
Day-to-day operations
TPS, CRM, ERP
Decision-makings
DSS, data warehouse
Strategic plans

3. Definitions Database: organized collection of logically related data
A group of related files
Data: stored representations of meaningful objects and events
Structured: numbers, text, dates
Unstructured: images, video, documents
Information: data processed to increase knowledge in the person using the data
Metadata: data that describes the properties and context of user data

4. Example of Metadata

5. Traditional File-Based Systems
A collection of application programs that perform services for the end-users. Each program defines and manages its own data.

6. Example

7. Limitations of the File-Based Approach
Duplication of data
Data inconsistency
Limited data sharing
Program-data dependence
When file structure changed, all programs that access the file must be modified to conform to the new file structure.
The definition of the data is embedded in the program.
Fixed queries
No facilities for asking unplanned, ad hoc queries

8. Problems with Program-Data Dependency
Each application program needs to include code for the metadata of each file
Each application program must have its own processing routines for reading, inserting, updating, and deleting data

9. Example: Comma-Delimited File
It stores each data item with a comma separating each item and places double quotes around string fields.
Student file with fields: SID, Sname, and GPA
“S5”, ”Peter”, 3.0
“S1”, “Paul”, 2.5
Questions:
How many students?
What is average GPA?

10. Sequentially Accessing the Student File to Compute Average GPA
Dim fileNumber, stCounter As Integer
Dim SID, SNAME As String
Dim gpa, sumGpa As Double
fileNumber = FreeFile()
FileOpen(fileNumber, "c:\stdata.txt", OpenMode.Input)
Do While Not EOF(fileNumber)
Input(fileNumber, SID)
Input(fileNumber, SNAME)
Input(fileNumber, gpa)
sumGpa += gpa
stCounter += 1
Loop
MessageBox.Show(sumGpa / stCounter.ToString)

11. Database Approach Central repository of shared data
The database holds not only the data but also a description of the data.
System catalog (repository , data dictionary, or metadata)
A central location where data descriptions are stored.
Data about data
Program-data independence

12. Advantages of the Database Approach
Program-data independence
The separation of data descriptions from the application programs that use the data.
Allows the data to change without changing the application programs.
Planned data redundancy
Improved data consistency
Improved data sharing
Enforcement of standards

13. Database Management System (DBMS)
A software that enables users to define, create, maintain, and control access to the database.
Data Definition Language (DDL)
Data Manipulation Language (DML)
Control access:
Security, integrity, concurrent access, recovery, support for data communication, etc.
Utility services
File import/export, monitoring facilities, etc.
Support Ad Hoc queries

14. Database Management System
A software system that is used to create, maintain, and provide controlled access to user databases
Order Filing
System
Central database
Contains employee,
order, inventory,
pricing, and
customer data
Invoicing
System
DBMS
Payroll
System
DBMS manages data resources like an operating system manages hardware resources

15. Evolution of DB Systems

16. Database Schema External Schema Conceptual Schema Internal schema
User Views
Subsets of Conceptual Schema
Conceptual Schema
This level describes what data is stored in the database and the relationships among the data.
View of the data administrator
E-R models
Internal schema
Logical schema
Underlying implementation and design
Relational table design
Physical Schema
File organizations, indexes

17. Figure 2-7 Three-schema architecture
Different people have different views of the database…these are the external schema
The internal schema is the underlying design and implementation

18. Data Independence
Data independence means that upper levels are unaffected by changes to lower levels.
Logical data independence
Changes to the conceptual level, such as the addition of new entities, attributes, or relationships, should be possible without having to change the existing external level design.
Physical data independence
Changes to the physical level, such as using a different file organization, indexes, should be possible without having to change the conceptual level design.

19. Three-Level Example Employee Entity
Conceptual design:
Employee entity with attributes: EmpID, EmpName, DateOfBirth, Salary, and Sex.
Internal level:
Logical schema:
EmpID – 4 characters
EmpName – 30 characters
DateOfBirth – Date field 8 bytes
Salary – Number(7,2)
Sex – 1 character
Physical schema:
Record size = = 50 bytes
Sequential file with index on EmpID field
External level:
EmpAgeView:
EmpID, EmpName, Age=Year(Today()) – Year(DateOfBirth)
EmpSalaryView: EmpID, EmpName, Salary

20. Benefits of Using Views
Views provide a level of security.
Views provide a mechanism to customize the appearance of the database.
Views provide a consistent, unchanging picture of the database, even if the underlying database is changed.

21. Database Application
It is a program that interacts with the database at some point in its execution by issuing an appropriate request (typically an SQL statement) to the DBMS.
Database programming

22. The Range of Database Applications
Personal databases:
Desktop, PDA/Smart Phone
Workgroup databases
Departmental/divisional databases
Enterprise database
Enterprise Resource Planning (ERP)
Integrate all enterprise functions (manufacturing, finance, sales, marketing, inventory, accounting, human resources)
Data Warehouse
Integrated decision support system derived from various operational databases

23. The three components in a database application
1. Presentation – user interface
Menus, forms, reports, etc
2. Processing logic
Business rules
3. Database

24. Categories of Database Applications
One-Tier
Legacy online transaction processing
PC database application
Two-Tier client/server
Client-based presentation.
Processing logic is buried either inside the user interface on the client or within the database on the server, or both.
Three-Tier, N- tier
Processing logic is separated from the interface and database.

25. Database Server: A high processing power computer with advanced DBMS.
SQL queries
Client
Database Server
Results
Database Server: A high processing power computer with advanced DBMS.
Client: A PC that runs database applications.
SQL interface.

26. Client Functions Manages the user interface.
Accepts and checks syntax of user input.
Implements business rules.
Generates database requests and transmits to server.
Passes response back to user.

27. Database Server Functions
Checks authorization.
Accepts and processes database requests from clients.
Ensures integrity constraints not violated.
Performs query/update processing and transmits response to client.
Provides concurrent database access, transaction management, and recovery control.

28. The Web as a Database Application Platform
Three-tier architecture
Browser, web server, database server, processing logic
Advantages:
Cross-platform support
Graphical user interface

29. Figure 2-9 Three-tiered client/server database architecture

30. Major Database Management Activities
Creating database
Updating database
Querying database

31. Creating Database Analysis Design
System analysis
Data Flow Diagram, UML
Data modeling
ERD
Design
Maps the data model on to a target database model.
Implementation: Efficiently store and retrieve data
File organization and index

32. Two Approaches to Database and IS Development
SDLC
System Development Life Cycle
Detailed, well-planned development process
Time-consuming, but comprehensive
Long development cycle
Prototyping
Rapid application development (RAD)
Cursory attempt at conceptual data modeling
Define database during development of initial prototype
Repeat implementation and maintenance activities with new prototype versions

33. Systems Development Life Cycle (see also Figures 2.4, 2.5)
Planning
Analysis
Physical Design
Implementation
Maintenance
Logical Design

35. Updating Database Insertions, deletions, modifications
Update pattern:
Insertion only, no modification
Concurrent processing
Read/Write
Transaction management

36. Querying Database
Relational algebra
SQL
QBE

37. New Developments in Database
Object-Oriented database
Object-Relational database
Decision support with data warehouse
Web based database applications
XML database

38. Course Overview An introduction to the three-level database
Conceptual level:
Data modeling, ERD, Normalization
Physical level:
File organizations and index
External level
Relational algebra, SQL, QBE
Other database management technologies