Page 468 - Computer_Science_F5

(c) Un-Normalised Form (UNF)
Un- Normalization is a systematic
Un-Normalised Form (UNF)
process governed by clear rules
Create model Data throughout the data modeling stages.
It encompasses several normal forms,
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each defined by specific criteria. Key Chapter Eight: Databases and Database Management Systems
First Normalised Form (1NF) normal forms include First Normal
Form (1NF), Second Normal Form
Remove Repeating Attributes (2NF), and Third Normal Form (3NF),
aimed at eliminating anomalies such as
insertion, updating, and deletion issues
Second Normalised Form (2NF) once implemented on a dataset.
Remove Partial Dependencies
Additionally, the Un-Normalized Form
(UNF) serves as the initial starting point
prior to applying normalization rules. It
Third Normalised Form (3NF)
represents the preliminary stage before
Remove Transitive Dependencies delving into detailed descriptions of
common normal forms (1NF, 2NF, and
Figure 8.17: Objective of UNF, and Three 3NF), as illustrated in Figure 8.17 and
normal forms (1NF; 2NF; 3NF) shown in Table 8.6.

Table 8.6: An example of an unnormalised form table

emp_id emp_name emp_address emp_dept
101 Samson Madirisha DSM D001
101 Samson Madirisha DSM D002
123 Madina Wavu Kagera D890
166 Hashim Milango Mbeya D900
166 Hashim Milango Mbeya D004

In this unnormalized Table 8.6, there is an update anomaly. For instance, employee
Samson appears in two rows because he belongs to two different departments.
Updating Samson’s address requires changing both rows to maintain consistency;
otherwise, the data becomes incorrect. If one department’s address is updated but
not the other, the database would show conflicting addresses for Samson.

Additionally, this table may lead to an insert anomaly. If a new employee joins
without being assigned to any department (emp_dept does not allow nulls), inserting
their data into the table becomes impossible.

459
Student’s Book Form Five

Computer Science Form 5.indd 459 23/07/2024 12:34