1. Database Design and Introduction to SQL
DBS201
Database Design and Introduction to SQL

2. Introduction to Database Management

3. Terminology
Application: programs, data, procedures used for some purpose in an organization (eg financial, payroll, equipment maintenance, project management, …)
Database: an organized collection of related data for an application
DBMS (DataBase Management System): set of programs that manage (create, modify, secure, backup, restore, …) one or more databases (eg Access, DB2, Oracle, SQL Server)
Database Design: determining the structure (ie. schema) of the database required for the application

4. File Based Approach
Used in all manual systems and in early computerized systems
Duplicates data between applications (eg customer information stored in files for Sales, Customer Service, Billing, …)
Increased data maintenance
Can create data inconsistencies
Very difficult to fulfill requirements that involve data from more than one system

5. File Based (Non-database) Approach

6. Database Approach
Data for each application is stored in a database and managed by the DBMS
Data can only be accessed through the DBMS and not directly through the OS

7. Database Approach Advantages
Easier to combine data from more than 1 application
Ability to share data between applications can result in reduced data redundancy (reduced duplication and improved consistency of data)
Concurrency: Allows access to data by many different users at the same time
Centralized control of data by DBMS and DBA

8. Advantages of Database (ctd)
Improved security and recovery of data
Data integrity can be maintained through constraints
DBMS development tools reduce programming required
Application Flexibility and Data independence : Structure of data can be changed without having to change programs

9. Disadvantages of Database Approach
Complexity of DBMS software requires developers to have specialized skills
DBMS overhead: software cost, data storage requirements, processing requirements, DBA responsibilities
Greater reliance on reliability of 1 software product (as opposed to many different file-based applications)
Applications take more time to design
More complex to recover data

10. Sharing of Data between Applications using a DBMS

11. History of DBMS’s Mainframe DBMS’s have been used since the 1960s
Since the mid-1980s, DBMS’s on PCs possess many of the features of their mainframe counterparts
Evolution of DBMS models: Hierarchical, Network, Relational, Object-oriented, Object-relational

12. Hierarchical Database Model
Data is seen as a tree structure and can only be retrieved by navigating through hierarchy
A parent record can have many children but a child record can have only 1 parent record
Navigation is achieved through use of pointers physically stored with each record

13. Hierarchical Database Model
IBM’s IMS was one of first hierarchical DBMS’s
Still used by many large legacy OLTP(online transaction processing) applications
Good at handling large volumes of data that only need to be accessed using only predefined paths

14. Network Database Model
Next database model; product examples: IDMS, I-D-S
Data is seen as a network of records and relationships between these records
Data can only be accessed by navigating through defined relationships
Pointers physically stored with each record permit navigation
Can represent applications that can not be represented using hierarchical model (eg Henry’s Books)

15. Relational Database Model
Developed after network model
Based on mathematical set theory that ensures that data can be retrieved in any way required by an application
Data is stored in the form of 2 dimensional tables with no physical pointers
Data is related through common columns in separate tables
Product Examples: Oracle, DB2, SQL Server