Page 469 - Computer_Science_F5

Computer Science Lastly, there is a delete anomaly in this unnormalized table. If the company closes
department D890, deleting rows with emp_dept as D890 would also remove
employee Madina’s information because she is only assigned to that department.

To resolve these issues, it’s essential to normalize the data into the three normal
forms introduced earlier. Another example of an Unnormarised Table is shown in
FOR ONLINE READING ONLY
Table 8.7.

Table 8.7: Non-normalized table
Full name Address Movie_industry Sports
Ismail Makame Kijichi Hollywood and Bollywood Football and Basketball
Rehema Kiongwe Mnazi Moja Swahiliwood and Nollywood Netball
Muki Mohamed Mbagala Nollywood and Riverwood Cricket

Advantages of normalization First Normal Form (1NF)
(i) Normalization helps to reduce data As indicated in Figure 8.8, the objective
redundancy of this 1NF is to remove repeating
(ii) More incredible overall database attributes. This is done because the
organisation relation is in 1NF if it contains an atomic
(iii) Data consistency within the value, and an attribute of a table cannot
database hold multiple values. Instead must have
(iv) Much more flexible database
design only single-valued attributes.
(v) Enforces the concept of relational
integrity Also, 1NF disallows the multi-valued
attribute, composite attribute, and their
Disadvantages of normalization
(i) You cannot start building the combinations. For a table to be in the
database before knowing what First Normal Form, it should follow the
the user needs. following four rules:
(ii) The performance degrades when (i) It should only have single (atomic)
normalizing the relations to higher valued attributes/columns.
normal forms, that is, 4NF, and (ii) Values stored in a column should
5NF.
(iii) It is very time-consuming and be of the same domain.
challenging to normalize relations (iii) All the columns in a table should
of a higher degree. have unique names.
(iv) Careless decomposition may (iv) The order in which data are stored
lead to a bad database design and does not matter.
severe problems.

460
for Advanced Secondary Schools

Computer Science Form 5.indd 460 23/07/2024 12:34