1. Sample Table Standard Notation Entity name in uppercase
Accession Number
DeweyCode
Title
Author
Date
Published 88
121.9
Let’s Cook
Chan, C
1992
123
Electricity
Glendenning, V
1995
300
Riders
Cooper, J
657
200.00
Greek in 3 weeks
Stavros, G
1990
etc…
Standard Notation
BOOK(AccessionNo, DeweyCode, Title, Author,DatePublished)
Entity name in uppercase
Key field (unique identifier) is underlined
All attributes are shown in brackets, separated by commas
ANS ( Normaliziation)

2. Primary Keys
This is a field that is used to uniquely define a particular record or line in a table.
Since text fields e.g. surname can be repeated, primary keys are nearly always numeric fields.
They can include:
Membership number, product number, employee number, catalogue number, account number.
SECONDARY KEY
A secondary key is a field or attribute that is not necessarily unique but is used for example to sort or order the data. An example above might be the supplier name in the supplier table.
ANS ( Normaliziation)

3. Foreign Keys Video Table Video Rentals Table
This is a field in one table which is also the primary key of another table.
Foreign keys are used to establish a relationship between the main table and other subsidiary tables.
Customer Table
Customer ID
First Name
Surname
Address
Telephone number
Age
Gender
Video Table
Video ID
Video title
Rating
Film Genre
Date Released
Length of film
Rental price
Video Rentals Table
Video_Rental ID
Customer ID
Video ID
Date Rented
Date Returned
ANS ( Normaliziation)

4. Relational database
A RELATIONAL database. A relational database is one which allows more than one individual table (also called a relation) to be connected together.
ANS ( Normaliziation)

5. Linking Database Tables
One-to-many
Tables may be linked through the use of a common field.
This field must be a key field of one of the tables and is known as foreign key in the second table. In a Library database two tables book and Borrower and makes a relationship
Borrower
Book
borrows
If there is another table of Loan which attributes as below
LOAN( Association number, Borrower id, datedue
Borrower
Book
has
Loan
consisting of
ANS ( Normaliziation)

6. Linking Database
ANS ( Normaliziation)
Prepared by: Mazhar Javed Awan

7. Normalisation
Normalisation is a process used to come up with the best possible design for a relational database. Tables should be organised in such a way that:
No data is unnecessarily duplicated
Data is consistent throughout the database
Structure of each table is flexible enough to allow you to enter as many / few items as you want to
The structure should enable a user to make all kinds of complex queries relating data from different tables
ANS ( Normaliziation)

8. Sample data to be held in a database
Student number
Student name
Date of birth
Sex
Course number
Course name
Lecturer number
Lecturer name
12345
Heathcote,R M
EC6654,EC9011
EC4521
A Level Computing,
Math A level,
Physics
T345267
T223459
T318743
Glover,T
Todd,M
Chapman
22433
Head,J F
EC6654
AD6611
BM7634
A Level Computing
Art
French
T886554
T165555
Lowry,B
Burke,D
128867
Hargrave,R
This data should be split into two tables, STUDENT and COURSE, in standard database notation:
STUDENT(StudentNumber, StudentName, DateOfBirth,Sex)
COURSE(CourseNumber,CourseName,LecturerNumber,LecturerName)
Consider the problems of creating a relationship between these two tables.
A link has to made between common fields
ANS ( Normaliziation)

9. First normal form
Definition: A table is in first normal form if it contains no repeating attributes or groups of attributes.
Let’s look at a simple example of two entities STUDENT and COURSE.
A student can take several courses, and each course has several students attending. The relationship can be represented by the entity-relationship diagram:
STUDENT
COURSE
attends
There is a many-to-many relationship between entities STUDENT and COURSE
ANS ( Normaliziation)

10. Creating the relationship
We need a common field, but the problem is that because this is a many-to-many relationship, whichever table we put the link field into, there needs to be more than one field.
e.g. STUDENT (student number, student name, date of birth, sex, course number) is no good because the student is doing several courses, so which one would be mentioned?
Similarly, COURSE (course number, course name, lecturer number, lecturer name, student number) is no good either because each course has a number of students taking it.
How about allowing space for 3 courses on each student record? STUDENT (student number, student name, date of birth, sex, course1, course2, course3)
Why is this not a good idea?
ANS ( Normaliziation)

11. Creating the relationship
What we have engineered is a repeating attribute –
unacceptable in 1st normal form.
In other words, the field course number is repeated 3 times
The table is therefore NOT in first normal form. It would be represented in standard notation with a line over the repeating attribute:
STUDENT (student number, student name, date of birth, sex, course number)
To put the data into first normal form, the repeating attribute must be removed.
ANS ( Normaliziation)

12. Creating the relationship
In its place, the field course number becomes part of the primary key in the student table. The tables are now as follows:
STUDENT (student number, student name, date of birth, sex, course number)
COURSE (course number, course name, lecturer number, lecturer name)
Discussion: What is a primary key? Why does course number have to be part of the primary key?
ANS ( Normaliziation)

13. The situation so far: STUDENT COURSE student no. student name D.O.B.
sex
course no.
12345
Heathcote,R M
EC6654
22433
Head,J F
HM7756
AD1121
66688
Hargrave,R
BM3390
STUDENT
course no.
course name
Lecturer no.
lecturer name
EC6654
A-Level Computing
T345267
Glover,T
HM7756
A-Level Music
T773351
Reader,B
AD1121
Pottery
T876541
BM3390
HNC Business
T666758
Newman,P
COURSE
ANS ( Normaliziation)

14. Second Normal Form Only applicable if table has a compound key
A table is second normal form (2NF) if it is in first normal form and no column that is not part of the primary key is dependent on a portion of the primary key:
This may be said as: A table in 2NF contains no partial dependencies
The tables on the previous slide are not in 2NF because, for example, student name is dependent only on student number and not on course number
To put the tables in 2NF we need to introduce a third table to link the two entities
ANS ( Normaliziation)

15. The tables in 2nd Normal Form
STUDENT (student number, student name, date of birth, sex)
STUDENT_TAKES (student number, course number)
COURSE (course number, course name, lecturer number, lecturer name)
What we had with the two entities was a many-to-many relationship
This situation will always need a link table to create two one-to-many relationships
ANS ( Normaliziation)

16. Third Normal Form
A table in third normal form (3NF) contains no non-key dependencies
The COURSES table contains an attribute for lecturer number and also one for lecturer name.
Lecturer name is dependent on lecturer number (not on course number)
Therefore a new table should be created for LECTURER
ANS ( Normaliziation)

17. Normalised Files
STUDENT (student number, student name, date of birth, sex)
STUDENT_TAKES (student number, course number)
COURSE (course number, course name, lecturer number)
LECTURER (lecturer number, lecturer name)
This is the optimum way of holding this data, with no duplication.
The tables in Relational Databases should be in Third Normal Form
ANS ( Normaliziation)

18. Comparing flat-files with RDB
A relational database is able to create links between tables representing different entities such as STUDENT and COURSE, through the use of foreign keys.
A flat file system is not able to link tables
It is only useful for very simple databases which contain information about just one entity.
It is impossible to ‘normalise’ a database in a flat file system, since this involves correctly establishing links between tables
Flat-file systems do not have any of the sophisticated features of a full DBMS such as the ability to set individual user-access rights, or allow several people to access the database at the same time
ANS ( Normaliziation)