A student record holds StudentID, StudentName, TutorGroup and a repeating group of CourseCode, CourseTitle, TeacherID and TeacherName. Why is it unnormalised?

One student row carries several courses at once, which is a repeating group. The number of course columns would also have to change whenever a student took another course.

Convert that student record to first normal form.

Each course becomes its own row, with the student details repeated alongside it. The table becomes ENROLMENT(StudentID, StudentName, TutorGroup, CourseCode, CourseTitle, TeacherID, TeacherName) keyed on StudentID and CourseCode.

Why is a composite key needed after the conversion to first normal form?

StudentID alone repeats across several rows, one for each course taken. Only StudentID together with CourseCode identifies a single row.

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Data Structures: Arrays, Records and Hash Tables

Topic overview One-dimensional arrays and indexing Two- and three-dimensional arrays Manipulating arrays: insertion, deletion and searching Records and fields Arrays of records and record manipulation Hash tables, hashing and collisions Choosing and justifying a data structure

Stacks, Queues, Linked Lists and Trees

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Boolean Logic and Simplification

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Programming Paradigms and Computer Languages

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Databases, Normalisation and Entity Modelling

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SQL, Big Data and Distributed Systems

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Databases, Normalisation and Entity Modelling

First normal form

3 things to know
Component 2

Overview

Unnormalised table, rule for first normal form and non-atomic attribute and say how to fix it.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What does normalisation aim to achieve?

Key term

What is an unnormalised table?

Key term

State the rule for first normal form.

Questions from this subtopic

Each one with the model answer underneath.

1
What does normalisation aim to achieve?
Model answer
Normalisation organises data into tables so that each fact is stored exactly once. Redundancy is removed and the update, insertion and deletion anomalies are avoided.
2
What is an unnormalised table?
Model answer
An unnormalised table contains repeating groups, where one row holds several values of the same attribute. A student row listing three courses is unnormalised.
3
State the rule for first normal form.
Model answer
A table is in first normal form when it has no repeating groups and every attribute holds a single atomic value. Every row must also be uniquely identifiable.
4
A student record holds StudentID, StudentName, TutorGroup and a repeating group of CourseCode, CourseTitle, TeacherID and TeacherName. Why is it unnormalised?
Model answer
One student row carries several courses at once, which is a repeating group. The number of course columns would also have to change whenever a student took another course.
5
Convert that student record to first normal form.
Model answer
Each course becomes its own row, with the student details repeated alongside it. The table becomes ENROLMENT(StudentID, StudentName, TutorGroup, CourseCode, CourseTitle, TeacherID, TeacherName) keyed on StudentID and CourseCode.
6
Why is a composite key needed after the conversion to first normal form?
Model answer
StudentID alone repeats across several rows, one for each course taken. Only StudentID together with CourseCode identifies a single row.

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