The data has to be organized in the respective files. Going beyond the natural and simplistic efforts of assembling similar data into a single file (all staff details in an employee file, all inventory particulars in an item file, etc), the technique is called normalization - devised by noted computer scientist E.F.Codd - helps us to streamline the data files in a structured manner, as described below. You will observe a graded sophistication as the first normalization form, the second normalization form and so on up to the fifth normalization form followed by the Boyce Codd normalization form. We will take an example of organizing some of the details on personnel employed with some company. Please note that we will confine our discussion to just a few attributes and not tackle the comprehensive set of all the attributes. We will also limit these deliberations to the first three normal forms.
Elements here would be: Employee Code, Employee Name, Department Code, Department Name, and Code of the Head of Department, Qualification Code, Qualification, and Degree Title.
We start putting these entire fields in one and the same file called the employee file. As you can see, the qualification code and qualification degree title from a repeating group due to the possibility of multiple educational courses one might have completed. These repeating groups pose a problem, inasmuch as they cannot be predicted in count. They may make the record length variable and thus give rise to lack of uniformity of storage. Besides, the repeating groups also make the logic unstructured, since the process does not know how many qualifications one might have obtained.
Hence to reach the first normalized form, we have to shift the repeating group into a new file with employee code additionally referenced in that file.
The normalization technique removes various issues that would have cropped up in the process of add/change/delete of records in the data files. Such issues are referred to as insert anomaly, update anomaly and delete anomaly respectively. The intricacies of normalization and the fourth normal form, fifth normal form and Boyce-Codd normal form are beyond the scope of this book. Those who are interested may benefit from reading the classic books on DMBS written by C J Dare and another one by Korth and Silbersha. We will now move on to another useful and widely used technique of file design namely Entity Relationship Diagrams. It would be fitting now to have a little re-brushing of the entity relationship diagrams (ERD).
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