Prentice Hall, Database Systems Week 1 Introduction By Zekrullah Popal

2 Data vs. Information Data: Raw facts; building blocks of information Unprocessed information Information: Data processed to reveal meaning Accurate, relevant, and timely information is key to good decision making Good decision making is key to survival in global environment

3 Database definitions: Def 1: A shared collection of logically related data, designed to meet the information needs of multiple users in an organization. The term database is often erroneously referred to as a synonym for a “database management system (DBMS)”. They are not equivalent and it will be explained in the next section.

4 Database definitions (cont…) Def 2: A collection of data: part numbers, product codes, customer information, etc. It usually refers to data organized and stored on a computer that can be searched and retrieved by a computer program. Def 3: A data structure that stores metadata, i.e. data about data. More generally we can say an organized collection of information.

5 Database definitions (cont…) Def 4: A collection of information organized and presented to serve a specific purpose. (A telephone book is a common database.) A computerized database is an updated, organized file of machine readable information that is rapidly searched and retrieved by computer.

6 Database definitions (cont…) Def 5: An organized collection of information in computerized format. Def 6: A collection of related information about a subject organized in a useful manner that provides a base or foundation for procedures such as retrieving information, drawing conclusions, and making decisions. Def 7: A Computerized representation of any organizations flow of information and storage of data.

7 Types of Databases Single-user: Supports only one user at a time Desktop/Personal Databases Single-user database running on a personal computer Multi-user: Supports multiple users at the same time

8 Types of Databases ( continued ) Workgroup Multi-user database that supports a small group of users or a single department Enterprise Multi-user database that supports a large group of users or an entire organization

9 Location of Databases Centralized: Supports data located at a single site Distributed: Supports data distributed across several sites

10 Disadvantages of File Processing Program-Data Dependence All programs maintain metadata for each file they use Duplication of Data Different systems/programs have separate copies of the same data Limited Data Sharing No centralized control of data Lengthy Development Times Programmers must design their own file formats Excessive Program Maintenance 80% of information systems budget

11 Problems with Data Dependency Each application programmer must maintain their own data 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 Lack of coordination and central control Non-standard file formats

12 Figure 1-2 Three file processing systems at Pine Valley Furniture Duplicate Data

13 Problems with Data Redundancy Waste of space to have duplicate data Causes more maintenance headaches The biggest problem: When data changes in one file, could cause inconsistencies Compromises data integrity

14 SOLUTION: The DATABASE Approach Central repository of shared data Data is managed by a controlling agent Stored in a standardized, convenient form Requires a Database Management System (DBMS)

15 Database Management System DBMS manages data resources like an operating system manages hardware resources A software system that is used to create, maintain, and provide controlled access to user databases

16 Client/server system architecture

17 Elements of the Database Approach Enterprise Data Model Graphical model showing high-level entities and relationships for the organization and the relationship among those entities. Entity: an object or concept that is important to the business.

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19 One customer may place many orders, but each order is placed by a single customer  One-to-many relationship

20 One order has many order lines; each order line is associated with a single order  One-to-many relationship

21 One product can be in many order lines, each order line refers to a single product  One-to-many relationship

22 Therefore, one order involves many products and one product is involved in many orders  Many-to-many relationship

23 Elements of the Database Approach (cont…) Relational Databases Database technology involving tables (relations) representing entities and primary/foreign keys representing relationships

24 Relationships established in special columns that provide links between tables

25 Elements of the Database Approach (cont…) Use of Internet Technology Networks and telecommunications, distributed databases, client-server Database Applications Application programs used to perform database activities (create, read, update, and delete) for database users

26 Application program functions: inserting new data, updating existing data, deleting existing data, reading data for display

27 Advantages of Databases Program-Data independence The separation of data description (metadata) from application programs that use the data. Changing organization’s data with out changing application programs that process that data. Minimal data redundancy Previously separate data files are integrated into a single, logical structure. Some limited redundancy may be desirable to improve database performance.

28 Advantages of Databases (cont…) Improved data consistency By eliminating data redundancy we greatly reduce inconsistencies. e.g. customer address stored once Storage space is not wasted Increased productivity of application development Cost and time of new database application is reduced Using functions, using reports and forms

29 Advantages of Databases (cont…) Improved data quality Database designer can specify constraints Improved data accessibility Select * from product where product_name= “computer”; Reduced program maintenance Changes are easily accommodated e.g. adding new data items, changing data formats

30 Costs and risks of database approach New, specialized personals Hire individuals to design and implement, and administer databases Upgradation of personal if new technology comes to market Installation and management cost Install, new release and upgrades, costly software for security Conversion cost Legacy system: older application in an organization based on file processing system Legacy to modern

31 Costs and risks of database approach Explicit Backup and recovery Organizational conflicts

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33 Figure 1-9 Workgroup database with local area network

34 Figure 1-10 An enterprise data warehouse

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36 Components of the Database Environment CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing the database Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the database System Developers – personnel responsible for designing databases and software End Users – people who use the applications and databases

37 Figure 1-11 Components of the database environment

38 Evolution of DB Systems Flat files s s Hierarchical – 1970s s Network – 1970s s Relational – 1980s - present Object-oriented – 1990s - present Object-relational – 1990s - present Data warehousing – 1980s - present Web-enabled – 1990s - present