1. Relations, Keys, & Normalization
DBS201

2. Equivalent Terms: Relational Model Table-Oriented DBMS
Conventional File Systems
Conceptionally Repreesents
Table
File
Row
Record
Column
Field
Column Type
Data Type
Column Value
Field Value

3. What is a Relation? Rows contain data about an entity
Columns contain data about attributes of the entity
Cells of the table hold a single value
All entries in a column are of the same kind
Each column has a unique name
The order of the rows and columns is unimportant
No two rows may be identical

4. Types of Keys?
A key is one or more columns of a relation that is used to identify a row
A key can be unique or nonunique
In Employee relation Emp_No vs Department
Composite Key
Primary Key
Candidate Key
Surrogate Key
Foreign Key

5. Keys A key that contains two or more attributes Is a composite key
Keys that uniquely identify each row in a relation
Are candidate keys
The candidate key that is chosen as the key that will actually be used by the DBMS to uniquely identify each row in a relation
Is a primary key

6. Keys
An attribute that is a key of one or more relations other than the one in which it appears
Is a foreign key
Foreign keys are one or more fields in a dependent file that reference the primary key in a parent file

7. Surrogate Keys
A column with a unique, DBMS assigned identifier that has been added to a table to be the primary key
The unique values of the surrogate key are assigned by the DBMS each time a row is added and the values never change
PROPERTY(Street,City,Prov,Pcode,OwnerID)
PROPERTY(PropertyID,Street,City,Prov,Pcode,OwnerID)
Surrogate keys are short, numeric and never change
Ideal as a primary key

8. Primary Key? Example of Hockey Awards
Award PlayerName Pnumber Position Team Year
Best Defense Joe Wall Left Defense Toronto
Sy Stopp Right Defense Detroit
Pete Puck Left Defense Montreal 2001
Joe Wall Left Wing Toronto 2002
MostValuable Sam Scores Center Chicago Wayne Gret Center New York 2000
Joe Wall Left Wing Toronto 2002

9. Primary Key? Fill in all attributes
Example of Hockey Awards
Award PlayerName Pnumber Position Team Year
Best Defense Joe Wall Left Defense Toronto
Best Defense Sy Stopp Right Defense Detroit
Best Defense Pete Puck Left Defense Montreal
Best Defense Joe Wall Left Wing Toronto
MostValuable Sam Scores Center Chicago MostValuable Wayne Gret Center New York
MostValuable Joe Wall Left Wing Toronto
2. Step 2: Look for any column that has no value that is used in more than one row. We are looking for a column for which it’s value is UNIQUE. We first check to see if we can have a single attribute primary key.
No one column meets this criterion.

10. Step 3: Look for any pairs of columns which when concatenated produce a unique value.
Team + Year…………
Position + Team……..
Position + Year………
PNumber + Position….
PNumber + Team…….
PNumber + Year……..
PlayerName + PNumber …
PlayerName + Position……
PlayerName + Team………
PlayerName + Year……….
Award + PlayerName……..
Award + PNumber………...
Award + Position………….
Award + Team…………….
Award + Year……………..

11. Concatenated Primary Key
So Award + Year will be selected as the PK.
and the relation will be:
(Award, Year, PlayerName, PNumber, Position, Team)

12. Normalization Review

13. Normal Forms
1NF
2NF
3NF
Why is this done?

14. Two ways to get to 1NF – how did we do it last week?
CLASSLIST
SubjectCode
Section
InstNo
InstName
SubjectName
StudentNo
StudentName
DBS201 A
122
Russ Pangborn
Intro to DB
Terry Adams
Jack Chan B
323
Bill Gates
Frank Brown
Mary Wong
RPG544
RPGIV
Wendy Clark
Peter Lind
Write CLASSLIST in UNF
CLASSLIST [ SubjectCode, SectionCode, InstructorNo, InstructorName, SubjectName, {StudentNumber, StudentName} ]
A relation is in 1st normal form when the primary key determines a single value of each attribute for all attributes in the relation (i.e. the relation contains no repeating groups)
Two ways to get to 1NF – how did we do it last week?

15. CLASSLIST
SubjectCode
Section
InstNo
InstName
SubjectName
StudentNo
StudentName
DBS201 A
122
Russ Pangborn
Intro to DB
Terry Adams
Jack Chan B
323
Bill Gates
Frank Brown
Mary Wong
RPG544
RPGIV
Wendy Clark
Peter Lind
Add to key of unnormalized relation to insure primary key identifies 1 and only 1 value of each attribute in the relation
CLASSLIST [ SubjectCode, SectionCode, InstructorNo, InstructorName, SubjectName, StudentNumber, StudentName ]
CLASSLIST [ SubjectCode, SectionCode, StudentNumber, InstructorNo, InstructorName, SubjectName, StudentName ]

16. Method 2
Restate the original un-normalized relation without the repeating group
CLASSLIST [ SubjectCode, SectionCode, InstructorNo, InstructorName, SubjectName ]
Create a new relation consisting of key of original relation and attributes within repeating group and add to key to ensure uniqueness
CLASSLISTSTUDENT [ SubjectCodeFK1, SectionCodeFK1, StudentNumber, StudentName ]

17. 2nd Normal Form
A 1NF relation is in 2NF when the entire primary key is needed to determine the value of each non-key attribute (i.e. relation has no partial dependencies – attributes whose values can be determined by knowing only part of the key)

18. 1st Normal Form -> 2nd Normal Form
1NF Relations: CLASSLIST [ SubjectCode, SectionCode, InstructorNo, InstructorName, SubjectName ]
contains the partial dependency SubjectCode -> SubjectName
CLASSLISTSTUDENT [ SubjectCode, SectionCode, StudentNumber, StudentName ]
contains the partial dependency StudentNumber-> StudentName

19. 2NF
Create new relation(s) consisting of part of the primary key and all attributes whose values are determined by this part of the primary key:
SUBJECT [SubjectCode, SubjectName ]
STUDENT [StudentNumber, StudentName ]
Restate original relation(s) without partially dependent attributes:
CLASSLISTSTUDENT [ SubjectCodeFK1, SectionCodeFK1, StudentNumberFK2 ]
CLASSLIST [ SubjectCode, SectionCode, InstructorNo, InstructorName ]

20. 3Rd Normal Form
A 2NF relation is in 3NF when the primary key and nothing but the primary key can be used to determine the value of each non-key attribute (i.e. relation has no transitive dependencies – attributes whose values can be determined by knowing something other than the key)

21. 2NF -> 3NF 2NF Relations:
CLASSLISTSTUDENT [ SubjectCodeFK1, SectionCodeFK1, StudentNumberFK2 ] ,
CLASSLIST [ SubjectCodeFK, SectionCode, InstructorNo, InstructorName ] ,
SUBJECT [SubjectCode, SubjectName ]
STUDENT [StudentNumber, StudentName ]
. In CLASSLIST the Instructor Name is determined by InstructorNo so create the new relation:
INSTRUCTOR [InstructorNo, InstructorName ]
Remove the transitive dependency
CLASSLIST [ SubjectCodeFK, SectionCode, InstructorNoFK ]

22. Resulting 3NF Relations for ClassList Userview
Set of 3NF Relations for the Class List Userview:
CLASSLIST [ SubjectCode, SectionCode, InstructorNo ]
CLASSLISTSTUDENT [ SubjectCode, SectionCode, StudentNumber ]
SUBJECT [SubjectCode, SubjectName ]
STUDENT [StudentNumber, StudentName ]
INSTRUCTOR [InstructorNo, InstructorName ]
1 unnormalized userview will always result in 1 or more relations in 1NF
Each 1NF relation will result in 1 or more 2NF relations
Each 2NF relation will result in 1 or more 3NF relations
You can never lose (ie not include) an attribute – it must always be found in one of the relations at each step
You can never lose a relation

23. Normalize Remaining User views
Normalization process is then applied to each remaining user view (eg grade sheet, timetable request, …)
A set of 3NF relations is produced for each user view
Then 3NF relations from each user view are then integrated to form one complete set of relations for the application

24. similar attributes – Subject Code, Section, …
GradeSheet
SubjectCode
Section
Subject Name
InstName
Grade
Sem
Year
StudentNo
StudentName
DBS201 A
Database Design
Russ Pangborn S
2016
Terry Adams
RPG544
Advanced RPG
Justin Trudeau B+
SYS333 B
Systems Analysis
Donald Trump C+ F
DBT544
DB2
Steve Harper
MAP525
Mobile Devices W
2017
MCL544
Assembler
Cito Gaston
similar attributes – Subject Code, Section, …
Different attributes – Grade, Semester, Year
Missing attribute – Instructor Number
Taking this to 3NF will produce similar entities like STUDENT, INSTRUCTOR and different entities like GRADES
After the user views are in 3NF a merge would be done

25. Writing a relation from a verbal or written description
Write the DBDL for the following description: 
Each dentist’s office has a unique identifier for insurance companies. There is a mailing address for the office as well as the name of the head dentist. There are many patients and each patient has a unique identifier number.
1. List Attributes
OfficeNo, MailAddress, HeadDentist,PatientNo, PatientName

26. 2. Select Primary Key (unique identifier for each row)
Each dentist’s office has a unique identifier for insurance companies. There is a mailing address for the office as well as the name of the head dentist. There are many patients and each patient has a unique identifier number.
2. Select Primary Key (unique identifier for each row)
OfficeNo, MailAddress, HeadDentist,PatientNo, PatientName
3. Show mulit-valued dependencies
OfficeNo,MailAddress,HeadDentist,(PatientNo, PatientName)
Give the table a name
DentistsOffice [OfficeNo, MailAddress, HeadDentist, (PatientNo, PatientName) ]
We call this 0NF or UNF (Unnormalized Form) because there is a multi-valued dependency

27. Change from UNF to 1NF
DentistsOffice [OfficeNo, MailAddress, HeadDentist, (PatientNo, PatientName) ]
 Select the Primary Key for the multi-valued dependency.
Create a two-part primary key by concatenating the original PK with the PK of the multi-valued dependency
DentistsOffice [OfficeNo, PatientNo MailAddress, HeadDentist, PatientName ]

28. Change from 1NF to 2NF
DentistsOffice [OfficeNo, PatientNo MailAddress, HeadDentist, PatientName ]
Look for partial dependencies
MailAddress is dependent on OfficeNo
PatientName is dependent on PatientNo
OfficePatient[OfficeNo,PatientNo)
DentistsOffice[ OfficeNo, MailAddress,HeadDentist]
Patient[PatientNo,PatientName]
Already in 3NF

29. [Purchase#, date, (item#, quantity, unit_ price, tax code)] 1NF
Purchases at Shoppers Drug Mart-1111 Young Street Toronto are identified by a unique purchase # and a date on the bill. There can be several items and the purchase must record the item #, the quantity, the unit price, a tax code for each item, and the total price.
 UNF
[Purchase#, date, (item#, quantity, unit_ price, tax code)]
1NF
Item# is the Primary Key of the multi-valued dependency.
[ Purchase#, item#, date, quantity, unit_ price, tax code]

30. PurchaseItem[ Purchase#, item#, quantity] Purchase[ Purchase#, date ]
Purchases at Shoppers Drug Mart-1111 Young Street Toronto are identified by a unique purchase # and a date on the bill. There can be several items and the purchase must record the item #, the quantity, the unit price, a tax code for each item, and the total price.
 2NF
PurchaseItem[ Purchase#, item#, quantity]
Purchase[ Purchase#, date ]
Item[ item#, unit_ price, tax code]

31. Normalization Abstract Example
For the following un-normalized relation:
RELN1[A, B, {C, D}, E, F, G]
where E can be determined by knowing only A, G can be determined by knowing only F and C can be used to determine D
1NF:
RELN1[A, B, C, D, E, F, G]
2NF:
RELN1[A, B, F, G]
RELN3[A, E]
RELN2[A, B, C, D]
3NF:
RELN1[A, B, F]
RELN4[F, G]

32. Nested Repeating Groups Example
Representation of a user view in UNF may result in nested repeating groups.
The process of resolving a repeating group must be performed starting with the outermost repeating group first to produce a temporary new relation containing a repeating group.
The process of resolving a repeating group must then also be performed on this temporary relation

33. STUDIOUS SENIORS ATTENDANCE REPORT
STUDIOUS SENIORS ATTENDANCE REPORT
Class# Class Name Room Member# Name Date Attendance
1234 Ballroom Dancing Jane Smith Sept Y
Sept Y
1234 Ballroom Dancing Bill Smith Sept Y
Sept N
1234 Ballroom Dancing Paul Woo Sept N
1234 Ballroom Dancing Mary Lu Sept Y
2245 Basket Weaving Mary Lu Sept N
Sept Y
3122 Italian Cooking Mary Lu Sept Y
Sept Y
3122 Italian Cooking Jane Smith Sept Y Sept 22 N
UNF?
ATTLIST [Class#,ClassName,Room, {Member#, Member_Name, {Date, Attendence} }]

34. UNF
ATTLIST [Class#,ClassName,Room, {Member#, Member_Name, {Date, Attendence} }]
1NF
ATTLIST(Class#,Member#,Date, ClassName,Room, Member_Name , Attendence)
2NF
MEMBER(Member#, Member_Name)
CLASS(Class#, ClassName,Room,)
ATTLIST(Class#,Member#,Date, Attendence)