Nowadays computers are extensively used to store and retrieve information.Offices are using computers to handle files which stores a variety of information.when needed,we get information from the files.The term database is used to refers to one or more related files.The files are now stored in magnetic memory.There is no need of paper to store information.Information can be seen on the computer screen;when required prints are taken out.Information from one office to another can be transmitted by electronic mail system.
To handle files database management packages are widely used.Suppose computer stores information in a file regarding students:
name of the students,roll number,marks subject wise,total marks,percentage of total marks,class awarded etc.Now some one asks computer to print the name of the students who have secured total marks 75% and above,one can ask to print the name of the students who have secured the highest marks in different subjects.Someone may provide roll number or name of the student and ask to print his marks sheet.
The database package not only stores information and supplies information,but also makes computation on data to supply certain information. Actually,in the above example,the total marks,percentage of marks,average etc..are calculate and then stored in tabulated form by the computer.Class is awarded by the computer.
A database management system can provide information from more than one related files.A user would like to have certain information which is not in a single file.Some information is in one file,some in other files.The program will search all the required information from different files and supply it to users.Take an example of records maintained by an advocate.He maintains two files.One file contains the records of different clients.It may be named as case file.It records client number,client identification number,name of the clients,address,phones number,amount due etc,He maintains another files which keeps the records of different cases.It may be named as case file.It records case number, identification number of the cases,identification number of the client of the different cases,type of the case,name of the opponent,attorney,court,judge,opening date,court date etc.Suppose the advocate wants information about which cases are to be taken up on a particular date,with the details of the cases the client file as well as the case file.The software package will collect information from both the files.The case file gives the information which cases are due on a particular date and their details.
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