Database management system
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The document discusses database management systems and file-based systems. It describes some common uses of databases like tracking inventory and processing credit card transactions. It outlines the problems with traditional file-based systems, like the difficulty answering queries that require data from multiple files. A database management system aims to solve these problems by storing all related data together and allowing complex queries across multiple tables.
Database management system
- 2. Objectives • Some common uses of database systems. • Characteristics of file-based systems. • Problems with file-based approach. • Meaning of the term database. • Meaning of the term Database Management System (DBMS) • Typical functions of a DBMS. • Major components of the DBMS environment. • Personnel involved in the DBMS environment. • History of the development of DBMS • Advantages and disadvantages of DBMS
- 3. About Data • The axiom "better data means better decisions" is more true today than ever. • No matter what business you're in, the success of your organization depends on accurate and timely information
- 4. First Thing First • What is data? • Why: you need data? • Where: is data reside? • Who: data belongs to? • How: is it a worthwhile data?
- 5. Information Hierarchy • Data: The raw Material of Information • Information: Data organized and presented in a particular manner. • Knowledge: Justified True belief. Information that can be acted upon. • Wisdom: Integrated knowledge. High level understanding
- 6. Some examples • Purchases from a supermarket • Bar code reader to scan each purchase. • Bar code reader is linked to an application program that uses the bar code to find out the price of the item from a product database. • This program reduces the number of such items in stock and displays the price on the cash register. • If the reorder level falls below a specified threshold, the database system may automatically place an order to obtain more stocks of that item.
- 7. Credit Card Example • Purchases using your credit card • Assistant normally checks you have sufficient credit left to make the purchase. This can be done on the telephone or may be done automatically by a card reader linked to a computer system. • There is a database somewhere that contains information about the purchases you have made on your credit card. • To check your credit there is a database application program that uses your credit card number to check that the price of the goods you wish to buy together with the sum of the purchases you have already made this billing period is within your credit limit.
- 8. Credit Card Example (conti..) • After confirmation of the purchase the details of the purchase are added to this database. • The application program also accesses the database to check that the credit card is not on a list of stolen credit cards before authorizing the purchase. • There are other application programs to send out monthly statements to each credit card holder and to credit accounts when payment is received
- 9. Traditional File-Based Systems • The file-based system is the predecessor of the database system. • This approach is mostly obsolete but: • understanding the problems inherent in file based systems may prevent us from repeating these problems in our database systems, • understanding how the file system works is extremely useful when converting a file-based system to a database system.
- 10. File-Based Approach • DEFN: The File-based system is a collection of application programs that perform services for the end-users such as the production of reports. Each program defines and manages its own data. • These were an early attempt to computerize the manual filing system that most of us are familiar with. • Really only works well when the number of items to be stored is small. • It works adequately when there are large numbers and we have only to store and retrieve them
- 11. Terminology used in file-based systems • A file is simply a collection of records, which contain logically related data. • Each record contains a logically connected set of one or more fields, • where each field represents some characteristics of the real-world object that is being modeled.
- 12. When does the manual filing system break down? • The manual filing system breaks down when we have to cross-reference or process information in the files. • Example: A typical real estate agent’s office might have a separate file for each property for sale or rent, each potential buyer and renter, and each member of staff.
- 13. Real Estate Example ctd… • How easy would it be to answer these questions using this set up? • What flats do you have for rent within three kilometres of the city centre? • What is the average rent for a two-bedroom flat? • What is the total annual salary bill for staff? • How does last month’s turnover compare with the projected figure for this month? • What is the expected monthly turnover for next financial year?
- 14. University Management System • Typically, a university might have different departments: • Admission Department • Entry test, student enrolment, fee collection, course registration etc. • Examination Department • Exams announcements, student results etc • Employees Management Department. • Course allocation, salaries etc.
- 15. University Management System ctd… • Which students taking the course of IDS which is allocated to ‘Uzair Muhammad’? • How many students passed the prerequisite subject OOP taking course IDS. • Which students eligible for scholarship according to University criteria?
- 16. Data Processing Staff (DP) • The file-based system was developed in response to the needs of industry for more efficient data access. A decentralized approach was taken, where each department, with the assistance of Data Processing (DP) staff, stored and controlled its own data. • We will illustrate this using an example
- 17. Example Real Estate ctd.. • The Sales Department is responsible for selling and renting property. • The form that landlord has to fill out before property is marketed for rent is shown; • This gives details of rental property as well as owner (landlord) details.
- 18. • Sales Department also handles enquiries from clients (renters)Client Details form.
- 19. • With assistance of Data Processing (DP) Department, Sales Department creates an information system to handle renting the property • This consists of three files containing property, owner and client details
- 20. • Contracts Department is responsible for rental agreements. • Wheneveraclientagreesto rentapropertyaformisfille doutbyoneoftheSalesstaff whichispassedtotheContr actsDepartmentwhichallo catesaleaenumberandco mpletesthepaymentandre ntalperioddetails.