comp 2216 fortran programming · 2015-02-02 · 8 normal forms •if you can design your database...

1

Database Concepts and Applications

COMP 244

Normal Forms

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Normalization

• Normalization: The process of

decomposing unsatisfactory "bad"

relations by breaking up their attributes

into smaller relations.

• Normalization is carried out in practice

so that the resulting designs are of

high quality and meet the desirable

properties.

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Essence of Normalization

• Every normalized relation should have a single theme.

• Any relation with two or more themes should be split into two or more relations each having a single theme.

– We continue doing this for every relation with modification anomalies.

– Splitting relations into two or more new relations could result in creating Referential Integrity Constraints.

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Referential Integrity Constraints

How to

record the

fact that

Student

300

participates

in Scuba

Diving?

Activity SID

Football 100

Swimming 150

Squash 175

Swimming 200

Fee Activity

200 Football

50 Swimming

50 Squash

STUDENT-ACTIVITY ACTIVITY-COST

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Referential Integrity Constraints

Activity SID

Football 100

Swimming 150

Squash 175

Swimming 200

Scuba Diving 300

Fee Activity

200 Football

50 Swimming

50 Squash

No corresponding

row for Scuba

Diving in this table.

STUDENT-ACTIVITY ACTIVITY-COST

• It is the user’s requirements

• We have to record that fact in the design

Who should decide

if to allow adding

Scuba Diving in

STUDENT-ACTIVITY

without adding a

corresponding row

in ACTIVITY-COST?

6

Normal Forms

• The set of rules that govern the ways in which attributes can be arranged are called Normal Forms.

• Normal forms provide an increasingly more stringent set of design rules that relations must meet.

• The least stringent is the first normal form (called 1NF) and the most stringent is the domain/key normal form (called DK/NF).

• The normal forms are nested in a way to indicate that if a relation is in an inner normal form, then it meets the normal forms outside it.

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Normal Forms

First Normal Form (1NF)

Second Normal Form (2NF)

Third Normal Form (3NF)

Boyce-Codd Normal Form (BCNF)

Fourth Normal Form (4NF)

Fifth Normal Form (5NF)

Domain/Key Normal Form (DK/NF)

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Normal Forms

• If you can design your database to meet the 3NF, then you will have avoided the majority of database design problems.

• The Boyce-Codd and fourth normal forms were created to handle special situations that are less frequent.

• The fifth and domain/key normal forms are more of theoretical interest and are not considered as practical design objectives.

• Any form in the DK/NF normal form is guaranteed to be free of all modification anomalies.

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What is a Relation?

• A relation is a two-dimensional table with rows (records) and columns (fields).

• For a table to be a relation, it must meet certain restrictions: – The cells of the table must be single valued (i.e.,

no repeating groups or arrays).

– All the entries of a column are of the same type.

– Each column must have a unique name.

– Order of columns is insignificant.

– No two rows may be identical.

– Order of rows is insignificant.

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First Normal Form

• Any table that meets the definition of a relation is said to be in first normal form.

• Relations in first normal form suffer from modification anomalies.

• When we eliminate modification anomalies, the relation becomes in a different form (depending on which anomaly was removed).

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Borrower-

Name

Borrower-

Phone

BookTitle Author-

Name

Loan-

Date

Return-

Date

Fee

Nasra 993 The best two

recipes

Najma 08/05/2003 19/07/2003 0.300

Khalid 831 Cars at light speed Ahmed 15/08/2003 23/08/2003

Ihsan 359 The best two

recipes

Najma 01/09/2003 07/09/2003

Nasra 993 How to sleep in

class?

Naser 12/10/2003

Fatma 818 Cars at light speed Ahmed 12/10/2003 27/10/2003 0.250

The cells of the table must be single valued (i.e., no repeating groups or arrays). All the entries of a column are of the same

type. Each column must have a unique name. Order of columns is insignificant. No two rows may be identical. Order of rows is insignificant.

Is this table in first

normal form?

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How to put this table in first normal form?

Course

Code Course Name Section First Name Last Name Days Time Room Capacity

COMP101 Computer Skills 1 QASIM AL OBAIDAT

Sat 01:00 PM-01:50 PM

32-8 60 Sun 01:00 PM-01:50 PM

Mon 01:00 PM-01:50 PM

Tue 01:00 PM-01:50 PM

COMP101 Computer Skills 2 Zahir Al Abri

Sat 10:00 AM-10:50 AM

29A Not more than 40 Sun 10:00 AM-10:50 AM

Mon 10:00 AM-10:50 AM

Tue 10:00 AM-10:50 AM

COMP101L Computer Skills Lab 1 Zahir Al Abri Sun 08:00 AM-09:50 AM

8-6 30 Tue 08:00 AM-09:50 AM

COMP101L Computer Skills Lab 2 Naeem Al-Shukaili Sat 08:00 AM-09:50 AM

8-4 30 Mon 08:00 AM-09:50 AM

COMP101L Computer Skills Lab 3 Naeem Al-Shukaili Sun 08:00 AM-09:50 AM

8-1 30 Tue 08:00 AM-09:50 AM

COMP101L Computer Skills Lab 4 Naeem Al-Shukaili Sat 10:00 AM-11:50 AM

8-5 Reserved Mon 10:00 AM-11:50 AM

Is this table in first normal form?

This column does not contain values of the

same type. The solution is to add a new

column for the remarks.

These two columns contain multiple values for

the same record. The solution is to split each

record into multiple records.

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Course Code Course Name Section First Name Last Name Day Time Room Capacity Remark

COMP101 Computer Skills 1 QASIM AL OBAIDAT Sat 13:00 - 13:50 32-8 60

COMP101 Computer Skills 1 QASIM AL OBAIDAT Sun 13:00 - 13:50 32-8 60

COMP101 Computer Skills 1 QASIM AL OBAIDAT Mon 13:00 - 13:50 32-8 60

COMP101 Computer Skills 1 QASIM AL OBAIDAT Tue 13:00 - 13:50 32-8 60

COMP101 Computer Skills 2 Zahir Al Abri Sat 10:00 - 10:50 29A Not more than 40

COMP101 Computer Skills 2 Zahir Al Abri Sun 10:00 - 10:50 29A Not more than 40

COMP101 Computer Skills 2 Zahir Al Abri Mon 10:00 - 10:50 29A Not more than 40

COMP101 Computer Skills 2 Zahir Al Abri Tue 10:00 - 10:50 29A Not more than 40

COMP101L Computer Skills Lab 1 Zahir Al Abri Sat 08:00 - 09:50 8-5 30

COMP101L Computer Skills Lab 1 Zahir Al Abri Mon 08:00 - 09:50 8-5 30

COMP101L Computer Skills Lab 2 Alaa Aljanaby Sat 08:00 - 09:50 8-4 30

COMP101L Computer Skills Lab 2 Alaa Aljanaby Mon 08:00 - 09:50 8-4 30

COMP101L Computer Skills Lab 3 Naeem Al-Shukaili Sun 08:00 - 09:50 8-1 30

COMP101L Computer Skills Lab 3 Naeem Al-Shukaili Tue 08:00 - 09:50 8-1 30

COMP101L Computer Skills Lab 4 Naeem Al-Shukaili Sat 10:00 - 11:50 8-5 Reserved

COMP101L Computer Skills Lab 4 Naeem Al-Shukaili Mon 10:00 - 11:50 8-5 Reserved

Solution

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Second Normal Form

• A relation is in second normal form if

all of its non-key attributes are

dependent on all of the key.

– Second normal form is of concern in

relations that have composite keys.

An implication of this rule is that if a

relation has a single attribute as its

key, then it is automatically in its

second normal form.

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Second Normal Form - Example Borrower-

Name

Borrower-

Phone

BookTitle Author-

Name

Loan-

Date

Return-

Date

Fee

Nasra 993 The best two

recipes

Najma 08/05/2003 19/07/2003 0.300

Khalid 831 Cars at light speed Ahmed 15/08/2003 23/08/2003

Ihsan 359 The best two

recipes

Najma 01/09/2003 07/09/2003

Nasra 993 How to sleep in

class?

Naser 12/10/2003

Fatma 818 Cars at light speed Ahmed 12/10/2003 27/10/2003 0.250

• Functional Dependencies: • BorrowerName BorrowerPhone

• BookTitle AuthorName

• (BorrowerName, BookTitle, LoanDate) ReturnDate

• (BorrowerName, BookTitle, LoanDate) Fee

How to put this table in

second normal form?

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Solution

• From the functional dependencies, we

conclude that the relation has three

different themes:

– Borrowers information

– We conclude this from the functional

dependency:

• BorrowerName BorrowerPhone

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Solution



different themes:

– Books information

– We conclude this from the function

dependency:

• BookTitle AuthorName

18

Solution



different themes:

– Book Loans information

– We conclude this from the functional

dependencies:

• (BorrowerName, BookTitle, LoanDate)

ReturnDate

• (BorrowerName, BookTitle, LoanDate) Fee

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Solution

• This tells us that we need to split the original relation into 3 smaller relations:

• Each relation will hold information about only one theme:

– Borrowers: Holds information about borrowers.

– Books: Holds information about books.

– Loans: Holds information about book loans.

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Solution

BorrowerName BorrowerPhone

Nasra 993

Khalid 831

Ihsan 359

Fatma 818

Borrowers

Is this relation in second

normal form?

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Solution

BookTitle AuthorName

The best two recipes Najma

Cars at light speed Ahmed

How to sleep in class? Naser

Books


normal form?

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Solution

Borrower-

Name

BookTitle LoanDate Return-

Date

Fee

Nasra The best two recipes 08/05/2003 19/07/2003 0.300

Khalid Cars at light speed 15/08/2003 23/08/2003

Ihsan The best two recipes 01/09/2003 07/09/2003

Nasra How to sleep in class? 12/10/2003

Fatma Cars at light speed 12/10/2003 27/10/2003 0.250

Loans


normal form?

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How to put this table in 2NF?

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Step 1 – Identify Key

25


















Step 1 – Identify Key

26


















Step 2 – List All FDs

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Step 2 – List All FDs

• CourseCode CourseName

• FirstName LastName

• (CourseCode, Section) CourseName,

FirstName, LastName, Time, Room

• (CourseCode, Section, Day)

CourseName, FirstName, LastName,

Time, Room, Capacity, Remark

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Step 3 – Split Relation into Sub

Relations

• Themes:

– Courses

– Instructors

– Course-Sections

– Section-Capacities

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Code Name

COMP101 Computer Skills

COMP101L Computer Skills Lab

COMP151 Introduction to Algorithms

COMP222 Object-Oriented Programming

Courses


normal form?

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ID FirstName LastName

100 Qasem Al Obeidat

101 Zahir Al Abri

102 Neem Al-Shukaili

103 Alaa Aljanaby

Instructors


normal form?

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Course Code Section Time InstructorID Room

COMP101 1 13:00 - 13:50 100 32-8

COMP101 2 10:00 - 10:50 101 29A

COMP101L 1 08:00 - 09:50 101 8-5

COMP101L 2 08:00 - 09:50 103 8-4

COMP101L 3 08:00 - 09:50 102 8-1

COMP101L 4 10:00 - 11:50 102 8-5

Course-Sections


normal form?

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Course Code Section Day Capacity Remark

COMP101 1 Sat 60

COMP101 1 Sun 60

COMP101 1 Mon 60

COMP101 1 Tue 60

COMP101 2 Sat Not more than 40

COMP101 2 Sun Not more than 40

COMP101 2 Mon Not more than 40

COMP101 2 Tue Not more than 40

COMP101L 1 Sat 30

COMP101L 1 Mon 30

COMP101L 2 Sat 30

COMP101L 2 Mon 30

COMP101L 3 Sun 30

COMP101L 3 Tue 30

COMP101L 4 Sat Reserved

COMP101L 4 Mon Reserved

Section-Capacities

4


normal form?

33

Third Normal Form

• Second normal form can still suffer

from insertion and deletion anomalies.

• A relation is in third normal form if it is

in second normal form and has no

transitive dependencies.

– Transitive dependency occurs when:

• Key Attribute N

• Attribute N Attribute M

• This means that indirectly (Key Attribute M)

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Example

Fee Activity SID

200 Football 100

50 Swimming 150

60 Squash 175

50 Swimming 200

ACTIVITY

• Functional

Dependencies:

• SID Activity

• Activity Fee

• SID Fee

(transitive

dependency) • Suffers from:

– Insertion anomaly

– Deletion anomaly

Each student is allowed to register for only one activity.

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Solution

• The problem with this relation is that it

records information about two themes:

– Activities that students can participate in.

– Cost of each activity.

• The solution is to split the relation into

two relations: – STUDENT-ACTIVITY

– ACTIVITY-COST

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Solution

Activity SID

Football 100

Swimming 150

Squash 175

Swimming 200

STUDENT-ACTIVITY

Is this relation in second normal form?

Is this relation in third normal form?

37

Solution

Fee Activity

200 Football

50 Swimming

60 Squash

ACTIVITY-COST

Is this relation in second normal form?

Is this relation in third normal form?

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Boyce-Codd Normal Form

• A relation is in Boyce-Codd normal form if the relation is in third normal form and every determinant is a candidate key.

– Candidate keys are collections of two or more attributes each of which can be used as a key.

– The candidate key that will be selected as the key for the relation is called the primary key.

39


SID Major AdvisorName

100 Math Naser

150 Psychology Wafa

200 Math Moza

250 Math Naser

300 Psychology Ishaq

300 Math Moza

ADVISOR

• For this relation:

– A student can have one or more majors

– A major can have several faculty members as advisors

– Each faculty member advises in only one major

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SID Major AdvisorName

100 Math Naser

150 Psychology Wafa

200 Math Moza

250 Math Naser

300 Psychology Ishaq

300 Math Moza

ADVISOR

• Candidate Keys:

– (SID, Major)

– (SID, AdvisorName)

• Functional Dependencies:

• (SID, Major) AdvisorName

• (SID, AdvisorName) Major

• AdvisorName Major

• Suffers from:

– Deletion anomaly

– Insertion anomaly

This is a determinant

that is not a candidate

key.

41


Major Advisor-Name

Math Naser

Psychology Wafa

Math Moza

Psychology Ishaq

ADVISOR-SUBJECT

SID Advisor-

Name

100 Naser

150 Wafa

200 Moza

250 Naser

300 Ishaq

300 Moza

STUDENT-ADVISOR

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• A relation in Boyce-Codd normal form

has no anomalies in regards to

functional dependencies.

– It was discovered that anomalies can arise

from situations other than functional

dependencies.

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Fourth Normal Form

SID Major Activity

100 Math Swimming

100 Accounting Tennis

150 Math Jogging

STUDENT

• Consider the following situation: – A student can enroll in one or more majors

– A student can participate in one or more activities

– Major and Activity are independent of each other

• This relation is misleading: – One might think that student

100 engages in Swimming when he is majoring in Math and engages in Tennis when he is majoring in Accounting.

• Such interpretation is not logical since the student is majoring in Math and Accounting at the same time.

44

Fourth Normal Form

SID Major Activity

100 Math Swimming

100 Accounting Swimming

100 Math Tennis

100 Accounting Tennis

100 Math Skiing

100 Accounting Skiing

150 Math Jogging

STUDENT

• Proposed Solution:

• Suffers from:

– Update anomaly (too much

updating needs to be done to

make a simple change in the

data)

If a student adds a

major, we must add a

tuple for each of the

student activities.

Similarly, if a student

adds an activity, we

must add a tuple for

each of the student

majors.

If a student drops

from one major, then

we must delete all

records that have

that major for this

student.

• This relation contains

Multi-Valued Dependencies:

• SID Major

• SID Activity

• Multi-Valued Dependencies: lead to

modification anomalies

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Fourth Normal Form

• In general, multi-valued dependency exists

when a relation has at least three attributes,

two of them are multi-valued, and their

values depend on only the third attribute.

• If a relation has attributes A, B, and C, then a

multi-valued dependency exists if:

– A B (A determines multiple values of B)

– A C (A determines multiple values of C)

– B and C are independent of each other

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Fourth Normal Form

SID Major

100 Math

100 Accounting

150 Math

STUDENT-MAJOR

SID Activity

100 Skiing

100 Swimming

100 Tennis

150 Jogging

STUDENT-ACTIVITY

• Solution:

– Create two relations, each one storing data

for only one of the multi-valued attributes.

• A relation is in Fourth normal form if it is in

BCNF and has no multi-valued dependencies.

47

Fifth Normal Form

• Concern dependencies that are rather

obscure.

• It has to do with relations that can be

divided into sub-relations, but cannot

be reconstructed.

• The condition under which this

situation arises has no clear, intuitive

meaning.

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Domain/Key Normal Form

• Was published in 1981 by R. Fagin.

• It guarantees that any relation in DK/NF

has no modification anomalies.

• It also guarantees that any relation

having no modification anomalies is in

DK/NF.

– Implies no higher normal form is needed.

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• Involves only the concepts of key and domain which are supported by most DBMS products. – A key is a group of one or more attributes that

uniquely identify a row.

– A domain is a description of the attribute’s allowed values.

• Physical description: The set of values the attribute can have.

• Logical (or semantic) description: The meaning of the attribute.

– A constraint is a restriction, or rule, that governs which data can be stored in a relation.

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• Examples of valid constraints:

– Edit rules

– Intra-relation constraints

• Constraints that govern relationships among

attributes of the same relation

– Inter-relation constraints

• Constraints that govern relationships among

attributes of different relations

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• Examples of excluded constraints:

– Constraints pertaining to changes in data

values

– Time-dependent constrains

• “Salary of current period can never be less

than salary of the prior period”.

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• There is no known algorithm for

converting a relation to DK/NF.

– It is not even known which relations can

be converted to DK/NF.

• Finding or designing DK/NF relations is more

of an art than a science.

53


• Example

– STUDENT (SID, GradeLevel, Building, FEE)

• Key: SID

• Constraints: Building Fee

• SID must not begin with digit 1

– Domain Definitions:

• SID CDDD where C is decimal digit

not = 1; D = decimal digit

• GradeLevel (“FR”, “SO”, “JR”, “GR”)

• Building CHAR(4)

• FEE DEC(4)

54


• Example (cont.)

– Relations and Key Definitions

• STUDENT (SID, GradeLevel, Building)

– Key: SID

• BUILDING-FEE (Building, Fee)

– Key: Building

55

Design Trade-Offs

• It is sometimes better to leave a relation in its un-normalized form because of simplicity and efficiency.

• Example: – CUSTOMER (CustomerNumber, CustomerName,

City, State, Zipcode) • CustomerNumber can be used as the key

• Zipcode (City, State)

– Possible Normalized Solution: • CUSTOMER (CustomerNumber, CustomerName,

Zipcode)

• CODE (Zipcode, City, State)

56

Design Trade-Offs

• There are sometimes more than one

normalized solution to the same un-

normalized relation.

• Example:

– COLLEGE (CollegeName, Dean,

AssistantDean)

• Each college can have from one to three

assistant deans

• (CollegeName, AssistantDean) is the key

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Design Trade-Offs

• Possible Normalized Solutions:

– Solution 1:

• DEAN (CollegeName, Dean)

• ASSITANT-DEAN (CollegeName, AssistantDean)

– Solution 2:

• COLLEGE (CollegeName, Dean, AssistantDean1,

AssistantDean2, AssistantDean3)

• CollegeName is the key

• Problem in searching (e.g., searching for all assistant

deans with a specific name)

comp 2216 fortran programming · 2015-02-02 · 8 normal forms •if you can design your database...

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