Introduction to Database Management System Objective This unit will cover following topics: * Definition of a database. * Difference between relational database and file system. * Advantages of Relational Database. * Tools for maintaining and retrieving data from a relational database. At the completion of this unit the learner will be able to : * Differentiate between a database and file system. Introduction to Database A database is a collection of related information. For example, a phone book is a database of names, addresses and phone numbers.
A data file is a single disk file that stores related information on a hard disk or floppy diskette. For example, a phone book database would be stored in a single data file. A Database Management System (DBMS) is a software tool that facilitates creating, maintaining, and manipulating an information database. The two types of DBMS software are: * Relational * Flat file Relational Database Software Relational database software allows the user to work with several database files at the same time and share information across the files.
For example, to implement an accounting database system, one requires relational capabilities to link together information that is stored in the different files. An example of a relational database software would be Microsoft Access, Oracle, Sybase and Paradox. Flat-file Database Software A flat-file database program, allows the user to create many databases but lets him/her work with only one file at a time. Using a flat -file database program, one can create simple applications such as mailing list databases or personnel files. Advantages of the database approach over traditional file-processing systems
Following are some of the advantages of using a database over a traditional file-processing system: * Potential for enforcing standards. * Flexibility. * Reduced application development time. * Availability of up-to-date information to all users. * Economies of scale. Benefits of a Relational Database Following are some of the advantages of a relational database: * Data can be easily accessed. * Data can be shared. * Data modeling can be flexibility. * Data storage and redundancy can be reduced. * Data inconsistency can be avoided. * Data Integrity can be maintained. Standards can be enforced. * Security restrictions can be applied. * Independence between physical storage and logical data design can be maintained. * High-level data manipulation language (SQL) can be used to access and manipulate data. A Relational database stores data is tables. The data stored in a table is organized into rows and columns. Each row in a table represents an individual record and each column represents a field. A record is an individual entry in the database. For example, each person’s name, address, and phone number is a single record of information in a phone book.
Whereas a “field” is a piece of information in a record. For example, you can divide a person’s record in the phone book into fields for their last name, first name, address, city and phone number. Queries A query is a quick method provided by DBMS programs to search a database and retrieve specific information. * For example, to find all the records from the phone book with last name Smith, the SQL query will be as follows: SELECT * FROM PhoneBook where LName = ‘SMITH’; Forms A form is used to view all fields for one record at a time. It can also be used to enter data into the database.
Following is an example of a form to enter information related to the spelling words. Reports Report tool is used to extract data from the database and present the information in the format that tables and forms to do not easily permit. * For example, reports can be used to group related record together and include summary totals for numeric fields. Reports can be created in a number of different presentation styles. Some of the most popular design styles are tabular (the most common), single record, and multi-record (for mailing labels). Following is an example of a report listing the student’s course, level and total score.