Page 447 - Computer_Science_F5

Computer Science (b) Network database model Because of this, the network database
model was the most extensively used
The network database model is designed
database model before the introduction
to flexibly represent objects and their
of the relational model.
relationships. Data is organised more
like a network in this model, and many
FOR ONLINE READING ONLY
parent nodes are allowed as shown
in Figure 8.3. The network model Stores
extends the hierarchical structure since
it provides many-to-many relationships Clerks Customers
to be managed in a tree-like structure
with multiple parents. Because more
associations are developed in this Transactions
database model as the data become
increasingly connected, accessing the
data becomes quicker and faster, and Items
redundancy is managed more efficiently Figure 8.3: An example of a network
than in the hierarchical approach. database model

(c) Relational database model
A relational database model represents data in which all items are organised into
two-dimensional tables known as relations. It is currently the most extensively used
model. In this paradigm, all data are kept in rows and columns in a table. Thus,
compared to network and hierarchical models, the basic structure of a relational
database model is simple, and it is readily scaled up because we may add as many
rows and columns as needed. For example, in the student table, shown in Figure 8.4
you can see columns (attributes or fields) and rows (tuples or records).

Attribe
Relation Name (column)

STUDENT
Name Student_ID Home_phone Address Office_Phone Age Gpa
Juma Rashid 120-88-3221 0773663288 123 Kusini 0772009923 25 3.2
Chausiku Mawazo 123-78-7689 0788712676 1454671 DSM NULL 18 2.7
Tuple Anna Majuto 888-08-7635 0625675412 543 Arusha NULL 19 3.5
(row) Kulwa Doto 762-87-2596 0754431298 45 Kahama 0713988776 27 3.1
Amina Karatasi 782-90-8754 0652870657 1276 Pemba 0772896514 23 4.1

Figure 8.4: The attributes and tuples of a student table

438
for Advanced Secondary Schools

Computer Science Form 5.indd 438 23/07/2024 12:34