1. UNIVERSITI TENAGA NASIONAL “Generates Professionals” MODULE 5 : Part 1 INTRODUCTION TO DATABASE

2. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Module Objectives At the end of the module, students should be able to: –describe the needs to database and define basic database terminologies. –explain the differences between file and database processing systems. –describe the DBMS and its common models  relational, network, hierarchical and object-oriented. –Describe the concept of data integrity –describe the parts of DBMS software including DDL, DML, query language and report generator. –describe the importance and needs to a database security, backup and recovery.

3. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Needs to a Database The purpose of a database is to help people keep track of things. A database is like a file-cabinet, to store information. –Folders in a file cabinet can be arranged to hold data in some useful order, so are the records in a database  we can search for specific information, manage the information such as add, modify, delete and so on. a set of information related to a specific application.Database can be defined as a set of information related to a specific application. The classical database applications  the tracking of items like orders, customers, jobs, employees, phone calls, or other items of interest to a business person.

4. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Basic Database Terminologies Entity  a person, place object, event or concept in the user environment about which the organization wishes to maintain data –Some examples entities are Employee, Student, Building, Registration, Account, Course Table / File  a collection of related records, the storage entity for a database (Figure 5.1) –made up of records that contain data about a single thing, such as a person or a sales transaction. Figure 5.1: A Table

5. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Basic Database Terminologies Record  set of fields containing data about a person, place, or thing, a unit within the table (Figure 5.2). –Each record in a table contains related information about an entity. Field  a smaller unit within a record that contains a fact / attribute about the entity. –E.g. in customer record, one field might contain a customer’s name, another field might contain the customer ID. Figure 5.2: A Record

6. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Basic Database Terminologies Key  used to order, identify and retrieve the records in the database. –defined from one or more fields from a table(s). – E.g. Key in table Customer is CustomerID. Primary key is the unique identifier for a particular record, no two records can have the same key value. Secondary key is defined by information from one or more other fields within the database. –E.g. A secondary key is created from the FirstName and LastName fields. –A secondary key differs from a primary key in that it allows multiple occurrences of the same table.

7. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Files and Databases Traditionally, information systems were developed with a file processing approach Database approach creates separate files for each entity

8. UNIVERSITI TENAGA NASIONAL “Generates Professionals” File Processing Systems Groups of records are stored in separate files –each application had its own file –Data was not shared among applications –Separate programs process separate data. –Allow only one file at a time to be processed. –The information stored in one file cannot be linked to other files. (Figure 5.3) Employee Processing Application Employee File Payroll Processing Application Payroll File Employee File User Payroll File User Figure 5.3: Two File-Processing System

9. UNIVERSITI TENAGA NASIONAL “Generates Professionals” File Processing Systems The limitations: –Data are separated and isolated –Data are often duplicated –Application programs are dependent on file formats –Files are often incompatible with one another –It is difficult to represent data in user’s perspectives

10. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Database Processing Systems Database technology was developed to overcome the limitations of file- processing systems. Database processing programs will call DBMS (database management system) to access the stored data. DBMS is used to define, create, maintain and provide controlled access to the database. (Figure 5.4) Employee Processing Application Employee File DBMS User Figure 5.4: Relationship between application program and DBMS

11. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Database Processing Systems The advantages: Data independence - reduces the dependency of programs on file formats. All record formats are stored in the database itself and they are accessed by the DBMS, not by application programs. This will also minimizes the impact of data format changes on application programs. Integrated data - All data is stored in a single facility called database and it will maintain the consistency of the data in all applications. Reduced data redundancy - redundancy level is minimal when data is kept in only one place, less opportunity for discrepancies among multiple copies of the same data item. Data security - data security in database package is to protect the data from unauthorized individuals

12. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Database Models 4 common types of database models (Figure 5.5.) i.Hierarchical database ii.Network database iii.Relational database iv.Object-oriented database HierarchicalNetworkRelationalObject-oriented Figure 5.5: DBMS organizations Traditional database models developed to store text and numeric data

13. UNIVERSITI TENAGA NASIONAL “Generates Professionals” i). Hierarchical Model Arranges data in hierarchical “parent-child” relationship –Each parent record can have many child records –Each child record has only one parent record Complex and inflexible

14. UNIVERSITI TENAGA NASIONAL “Generates Professionals” ii). Network Model Arranges data in complex network of “parent-child” relationships –Each parent record can have many child records –Each child record can have many parent records Complex and inflexible

15. UNIVERSITI TENAGA NASIONAL “Generates Professionals” iii). Relational Model Data organized in table format –Columns represent fields –Rows represent records Tables related by primary/foreign key relationship Most current database development uses this model

16. UNIVERSITI TENAGA NASIONAL “Generates Professionals” iv). Object-Oriented Model Designed to deal with complex data types Focuses on the object –An object represents an entity –Represents data about that entity and the types of operations that change that entity Today newest type of database structure. In an OO-database, the result of a retrieval operation is an object of some kind, such as a document. Within this object are miniprograms that enable the object to perform tasks, such as displaying a graphic. OO-database can incorporate sound, video, text and graphics into a single database record.

17. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Data Integrity Refers to the degree to which data is accurate and reliable Integrity constraints – set of rules that all data must follow –If integrity constraints are not followed, the data is unreliable

18. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Integrity Constraints Define acceptable values for a field –For example, the value of a month cannot be greater than 12 Primary keys cannot be duplicated (unique) Foreign keys cannot be used unless they exist as a primary key –A SalesID that is used in the customer table must exist as a primary key in the salesperson table

19. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Database Management A Database Management System (DBMS)  allows you to create a database and enter, modify, and retrieve data as needed Nowadays, the features and functions of many DBMS have grown to the point that the DBMS itself can process the application. –They contain report writers, form generators that can be integrated into an application. available at all levels –Sophisticated systems for a mainframe environment –Inexpensive, easy-to-use personal computer systems

20. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Database Features 1.Data dictionary 2.Data maintenance 3.Data retrieval 4.Concurrency control 5.Security 6.Backup and recovery

21. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 1. Data Dictionary Stores data about the tables and fields within the database –For each table, it stores the table name and relationships to other tables –For each field, it records information about that field Also called a catalog

22. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 2. Data Maintenance Three basic operations –Adding new data –Modifying existing data –Deleting data Two methods for performing operations –Interacting directly with the DBMS –Using programs to access the data using special commands

23. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 3. Data Retrieval Involves extracting the desired data Two primary forms of data retrieval a)Queries b)Reports

24. UNIVERSITI TENAGA NASIONAL “Generates Professionals” a) Queries You present a set of criteria; the DBMS selects matching data from the database Use a query language i.Structured Query Language (SQL) is supported by most relational databases ii.Query-by-example (QBE) uses a graphical interface to generate the SQL iii.Display results in a table-like grid

25. UNIVERSITI TENAGA NASIONAL “Generates Professionals” b). Reports Provide a formatted presentation of data from the database –Allow you to group reports and total by group, if desired –Normally contain more data than queries Reports are designed with a report generator

26. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 4. Concurrency Control Manages simultaneous database users –If several users tried to update the same record at the same time, updates might not be processed correctly Employs a record-locking scheme –Once a user accesses a record, it is locked until the first update is complete

27. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 5. Security Many security features are built into most DBMS software –Users can be required to enter a user ID and password –Each user ID may have different access to the data Read-only – permits the user to look at the data but not change it Update – permits the user to make changes to the data No privileges – user can not read or update the data

28. UNIVERSITI TENAGA NASIONAL “Generates Professionals” 6. Backup and Recovery Backup – a copy of the database –Backups should be made periodically Recovery – replaces a damaged database with the good backup

29. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Parts of DBMS Software Data Definition Language (DDL) oIs used to define the structure or the schema of the database. oThe structure outlines the data to be included in the database. oEach field in a record must be defined with a name, a field length and a type. Data Manipulation Language (DML) oIncludes all the commands that enable the user to manipulate and use the database. oUser can view the data, add new records, delete records, sort the records and modify selected fields in a record.

30. UNIVERSITI TENAGA NASIONAL “Generates Professionals” Parts of DBMS Software Query Language oEnables user to ask specific questions of the database. oThe most popular query language is Structured Query Language (SQL) and today, it is used in database management systems on any platforms Report Generator oThe report generator helps the user to design and generate reports and graphs in printed form. oSome of the features that are easy to include with the report generator are: report headings, column headings, page numbers and totals.