Database normalisation
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Transcript of Database normalisation
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DATABASE NORMALIZATION
Disclaimer: This presentation is prepared by trainees of baabtra as a part of mentoring program. This is not official document of baabtra –Mentoring PartnerBaabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd
DATABASE NORMALIZATION
LEVELS OF NORMALIZATION
SOLVED EXAMPLE
CONTENTS
DATABASE NORMALIZATION
What is normalization????
Why normalize the database???
Strength and drawback of normalization..!!!
What is actually normalization???
The process of analyzing a given relational schema based on their functional dependencies and primary keys.
Why normalize database????
Minimizing redundancyAccuracyPerformance
Strength And Drawback of Databases...!!!!
Strength:Reduces RedundancyReduces errors
Drawback:No of tables increasesComplexity increases
LEVELS OF NORMALIZATION
1NF2NF3NF BCNF 4NF 5NF DKNF
Redundancy
Num
ber o
f Tab
les
Com
plex
ity
FIRST NORMAL FORM-1NF
A table is considered to be in 1NF if all the fields containonly scalar values
Example (Not 1NF)
Pk_Int_Book_id Vchr_bookname Vchr_author
111 Basic Electrical and Electronics Engineering
Storey,Huggies,Tomasi
121 EVS Venugopal,Vinod
After performing 1NF
Pk_int_book_id Vchr_Bookname Vchr_author
111 Basic Electrical and Electronics Engineering
Storey
111 Basic Electrical and Electronics Engineering
Huggies
111 Basic Electrical and Electronics Engineering
Thomasi
121 EVS Vinod
121 EVS Venugopal
Second Normal Form
For a table to be in 2NF, there are two requirements:
The database is in first normal form
All non_key attributes in the table must be functionally dependent on the entire primary key
Second Normal Form- Example
Database not in 2NF:
Pk_Vchr_Emp_name Pk_Vchr_emp_desig Int_Emp_Sal Vchr_emp_address
Paul Manager 60000 121,PK street,Mumbai
Ram Clerk 5000 111/114, Arumugam street, Chennai
Primary key : {vchr_emp_name,vchr_emp_desig}
Here the employee salary is dependant on both primary keys.Employee address is not dependant on employee designation.Hence it is not in 2NF
Second Normal Form- Example
Database after performing 2NF:Pk_Vchr_Emp_name
Pk_Vchr_emp_desig
Int_Emp_Sal
Paul Manager 60000
Ram Clerk 5000
Pk_Vchr_Emp_name Vchr_Emp_address
Paul 121,PK street,Mumbai
Ram 111/114, Arumugam street, Chennai
THIRD NORMAL FORM
For a table to be in 3NF, there are two requirements:
The table should be second normal form
No attribute is transitively dependent on the primary key
All non key attributes of a table must be functionally dependent on a candidate key.
There must be no interdependencies among non-key attributes
Third Normal Form- Example
Database not in 3NF:Pk_int_stud_id Vchr_stud_name Int_class_id Vchr_class_name
3457 Ashish 101 CS5
4332 Abhay 121 EC6
Primary key : {pk_vchr_emp_name}
Here Student name , and class_id depends on primary key pk_int_stud_id. The class name is but more dependant on the class_id (non-key) than stud_id.So there is a transitive dependency. Hence not in 3NF.
Third Normal Form- Example
Database after performing 3NF:Pk_int_stud_id Vchr_stud_name Int_class_id
3457 Ashish 101
4332 Abhay 121
Pk_Int_class_id Vchr_class_name
101 CS5
121 EC6
AN EXAMPLE TO SOLVEExam Management System-----------------------------------Users:
Admin Student
Admin ---------
Login View Profile Edit Profile Facility to manage student Facility to manage exam
Student----------
Attend exams View mark
Let us first list the required tables:
Login_tableUser_tableUser_type_tableExam_tableExam_qstn_tableQstn_option_tableStud_answer_table
SOLVING THE PROBLEM
Pk_int_login_id Vchr_username Vchr_password
1 Administrator Admin
2 Ashish Ashish123
3 Abhay abhay123
Login_table
User_table
Pk_int_user_id
Vchr_uname
Fk_int_ login_id
Dat_dob Vchr_place
Bln_status int_user_ type
1 Pratap 1 1867-05-01 Calicut 1 1
2 Ashish 2 1993-02-01 Banglore 1 2
3 Abhay 3 1992-03-11 Chennai 1 2
Pk_int_ type_id
Vchr_ utype
1 Admin
2 Student
User_type_table
Pk_int_exam_id Vchr_exam_name int_exam_duration(in hrs)
101 Basic C programming Test
1
102 Cpp Evaluation test 1
Exam_table
Exam_qstn_table
Pk_int_qstn_id Fk_int_exam_id Vchr_question Vchr_answer Int_marks
1111 101 Code1 21 5
1112 101 Code2 11122133 10
1113 102 Code3 131 5
1114 102 Code4 3333 10
Question_option_table
Pk_int_option_id Fk_int_qstn_id Vchr_option
1 1111 21
2 1111 22
3 1111 25
4 1112 11122133
5 1112 0
6 1112 11100000
7 1113 131
8 1113 100
9 1113 1
10 1114 3333
11 1114 0
12 1114 2222
Student_answer_table
Pk_int_answer_id
Fk_int_qstn_id fk_int_user_id Vchr_stud_answer
Int_mark_scored
116 1111 2 22 0
117 1112 2 11122133 10
118 1113 2 131 5
119 1114 2 3333 10
120 1111 3 21 5
121 1112 3 11122133 10
122 1113 3 131 5
123 1114 3 0 0
THANK YOU...
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