Cibm work shop 2chapter six


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Cibm work shop 2chapter six

  2. 2. 6.1 DATABASE BASICS6.1.1 What Is Database?A database can be thought of as a set of logically related files organized to facilitate access by one or more applications programs and to minimize data redundancy. This concept does not imply that all data relating to a company’s business should be contained on a single database, but simply that all records in a database should be related and that redundant data should be minimized. Databases make it possible for people to store, organise, retrieve, communicate, and manage information in ways that wouldn’t be possible without computers.
  3. 3. Computerized databases offer several advantages over their paper-and-pencil counterparts:Databases make it easier to store large quantities of information.Databases make it easier to retrieve information quickly and flexibly.Databases make it easy to organize and reorganize information.Databases make it easy to print and distribute information in a variety of ways.Database make it easier to incorporate changes easily and quicklyDatabase provides data security from unauthorized use
  4. 4. 6.1.2 Database AnatomyA database is composed of one or more files. A file is a collection of related information; it keeps that information together the way a drawer in a file cabinet does. (The term file sometimes causes confusion because of its multiple meanings. In this chapter, file refers specifically to a data file created by a database program.)A database file is a collection of records. A record is the information relating to one person, product, or event. Each discrete chunk of information in a record is called a field.The type of information a field can hold is determined by its field type. For example, the author field in the library database would be defined as a text field. The field specifying the number of copies of a book would be defined as a numeric field. A date-of- purchase field might be a date field.
  5. 5. 6.1.3 Database OperationsBrowsingThe challenging part of using a database is retrieving information in a timely and appropriate manner. One way to find information is to browse through the records of the database file just as you would if they were paper forms in a notebook. Most database programs include a variety of commands and capabilities that make it easy to get the information you need when you need it.
  6. 6. Database QueriesThe alternative to browsing is to ask the database for specific information. In database lingo, an information request is called a query. A query may be a simple search for a specific record or request to select all of the records that match a set of criteria. Once you’ve selected a group of records, you can browse through it, produce a printout, or do just about anything else you might do with the complete file.
  7. 7. Sorting DataSometimes it’s necessary to rearrange records to make the most efficient use of data. A sort command allows you to arrange records in alphabetic or numeric order based on values in one or more fields.Printing Reports, Labels, and Form LettersIn addition to displaying information on the screen, database programs can produce a variety of printouts. The most common type of database printout is a report—an ordered list of selected records and fields in an easy- to-read form.
  8. 8. Database programs can also be used to produce mailing labels and customized form letters. Most database programs don’t actually print letters; they simply export or transmit the necessary records and fields to word processors with mail merge capabilities, which then take on the task of printing the letters.Complex QueriesQueries may be simple or complex, but either way they must be precise and unambiguous. The exact method for performing a query depends on the user interface of the database software.
  9. 9. 6.1.4 Special-Purpose DatabasePrograms Many specialised database programs are sold as directories, geographic information systems, personal information managers (PIMs), or electronic organisers, automating some or all of these functions: address / phone book appointment calendar to-do list street atlas miscellaneous notes The user interface of personal information management software is especially important because of the constant interaction between the user a In many organisations, PIMs have been replaced by enterprise information systems such as Microsoft Outlook. In many organizations, PIMs have been
  10. 10. 6.2.1 From File Managers to Database Management Systems A file manager is a program that allows users to work with one file at a time. A true database management system (DBMS) is a program or system of programs that can manipulate data in a large collection of files, cross-referencing between files as needed. A database management system can be used interactively, or it can be controlled directly by other programs. With a database management system, there’s no need to store redundant information in every file. Instead a key field is shared by all files that use the same data. If redundant data changes, it need only be recorded in one place.
  11. 11. 6.2.2 What Makes a DatabaseRelational?To most users, a relational database program is one that allows files to be related to each other so that changes in one file are reflected in other files automatically. To computer scientists, the term relational database has a technical definition related to the underlying structure of the data and the rules specifying how that data can be manipulated.The structure of a relational database is based on the relational model—a mathematical model that combines data in tables. Other kinds of database management systems are based on different theoretical models, with different technical advantages and disadvantages.
  12. 12. Example of Database
  13. 13. 6.3.1 Real-Time ComputingThe earliest file management programs could only do batch processing, which required users to accumulate transactions and feed them into computers in large batches. These batch systems weren’t able to provide the kind of immediate feedback we expect today.Today disk drives, inexpensive memory, and sophisticated software have allowed interactive processing to replace batch processing for most applications. Users can now interact with data through terminals, viewing and changing values in real time. Batch processing is still used for printing periodic bills, invoices, and reports and for making backup copies of data files. But for applications that demand immediacy, such as airline reservations, banking transactions, and the like, interactive, multi-user database systems have taken over.
  14. 14. 6.3.2 Downsizing andDecentralisingUntil recently, most databases were housed in mainframe computers. But for a growing number of organisations, the traditional centralised database on a mainframe system is no longer the norm.Some companies use a client/server approach. Database software in client desktop computers works with files stored in central server databases on mainframes, minicomputers, or desktop computers. Some companies keep copies of all corporate data in an integrated data warehouse, which give users more access to enterprise data than the old-style centralised systems.Other companies use distributed databases that use data strewn out across networks on several different computers. From the user’s point of view, the differences between these approaches may not be apparent.
  15. 15. 6.3.2 Data MiningData mining is the discovery and extraction of hidden predictive information from large databases using statistical methods and artificial intelligence technology.6.3.4 Object-Oriented DatabasesMany computer scientists believe that the relational data model may be supplanted in the next decade by an object-oriented data model, and that most future databases will be object- oriented databases rather than relational databases. Instead of storing records in tables and hierarchies, object-oriented databases store software objects that contains procedures (or instructions) along with data. Object-oriented databases often are used in conjunction with object-oriented programming languages.
  16. 16. End Of Chapter SIXExample of Pastel Accounting database program below