Database Design


Historically files have been designed based on specific application. Payroll files are created containing all the data pertinent to a company’s payroll system. Similarly, individual files are created for use with the company’s personnel, accounts receivable, inventory, and other systems. If the data contained on these files are not carefully delineated, it is very much likely that the same data will appear on several of these files. In other words, these files would contain redundant data. For example, both a company’s personnel file and payroll file could contain the name and address of each employee. This would mean that a simple change of address would have to be processed twice and possibly three or four times, depending on the number of other files on which these data appear. Clearly, it would be more practical to have each employee’s name and address on one file from which it can be accessed by all pro6L’ams requiring these data. This would reduce the amount of redundant data and minimise the possibility that data contained on a file might be inaccurate. This is but one of the reasons that database technology was developed.

A database can be thought of as a set of logically related files organised to facilitate access by one or more application programs and to minimise data redundancy. In other words, a database can be defined as a stored collection of data, organised on the basis of relationships in the data rather than the convenience of storage structures. It is not a replacement of files.

Some general objectives in establishing a database are as follows,

  • Eliminate redundant data as much as possible.
  • Integrate existing data files.
  • Share data among all users.
  • Incorporate changes easily and quickly.
  • Simplify the use of data files.
  • Lower the cost of storing and retrieving data
  • Improve accuracy and consistency
  • Provide data security from unauthorised use
  • Exercise central control over standards.

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