10-08-2012, 12:27 PM
Databases
Databases.ppt (Size: 1.08 MB / Downloads: 314)
INTRODUCTION
Data storage traditionally used individual, unrelated files, sometimes called flat files. In the past, each application program in an organization used its own file. In a university, for example, each department might have its own set of files: the record office kept a file about the student information and their grades, the scheduling office kept the name of the professors and the courses they were teaching, the payroll department kept its own file about the whole staff and so on. Today, however, all of these flat files can be combined in a single entity; the database for the whole university.
Definition
Although it is difficult to give a universally agreed definition of a database, we use the following common definition:
Advantages of databases
Comparing the flat-file system, we can mention several advantages for a database system.
Less redundancy
In a flat-file system there is a lot of redundancy. For example, in the flat file system for a university, the names of professors and students are stored in more than one file.
Inconsistency avoidance
If the same piece of information is stored in more than one place, then any changes in the data need to occur in all places that data is stored.