1. Lecture Nine: Normalization
Introduction to Normalization: redundancy, anormalies?
1st – 3rd Normal Forms
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2. Objectives Purpose of normalization.
Problems associated with redundant data.
Identification of various types of update anomalies such as insertion, deletion, and modification anomalies.
How to recognize appropriateness or quality of the design of relations.
How functional dependencies can be used to group attributes into relations that are in a known normal form.
How to undertake process of normalization.
How to identify most commonly used normal forms, namely 1NF, 2NF, and 3NF
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3. Normalization
Normalization is defined as a technique for producing a set of well designed relations that measure up to a set of requirements which are outlined in various levels of normalization (or Normal Forms).
Most commonly used normal forms are first (1NF), second (2NF) and third (3NF) normal forms.
Normalization has the underlying aim of minimizing information redundancy, avoiding data inconsistency and preventing Update anomalies (insertion, deletion, and modification anomalies).
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4. Data Redundancy
Major aim of relational database design is to group attributes into relations to minimize data redundancy and reduce file storage space required by base relations.
Problems associated with data redundancy are illustrated by comparing the following Staff and Branch relations with the StaffBranch relation.
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5. Data Redundancy
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6. Update Anomalies
Relations that contain redundant information may potentially suffer from update anomalies.
Types of update anomalies include:
Insertion
Deletion
Modification.
Insertion Anomaly: Occurs when extra data beyond the desired data must be added to the database.
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7. Update anomalies: Insertion Anomaly
Until the new faculty member, Dr. Newsome, is assigned to teach at least one course, his details cannot be recorded.
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8. Update anomalies: Modification Anomaly
Modification Anomaly: Changing the value of one of the columns in a table will mean changing all the values that have to do with that column.
Employee 519 is shown as having different addresses on different records.
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9. Update anomalies: Deletion Anomaly
Deletion Anomaly: Occurs whenever deleting a row inadvertently causes other data to be deleted.
All information about Dr. Giddens is lost when he temporarily ceases to be assigned to any courses.
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10. Functional Dependency
Functional Dependency: Describes relationship between attributes in a relation.
If A and B are attributes of relation R, B is functionally dependent on A (denoted A  B), if each value of A in R is associated with exactly one value of B in R.
Diagrammatic representation:
Main concept associated with normalization.
Determinant of a functional dependency refers to attribute or group of attributes on left-hand side of the arrow.
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11. Functional Dependencies
Example
branchNo bAddress
Functional Dependencies
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12. Example - Functional Dependency
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13. Functional Dependencies
Example
Functional Dependencies
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14. Example Given TEXT we know the COURSE. TEXT ->COURSE
TEXT maps to a single value of COURSE
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15. The Process of Normalization
Formal technique for analyzing a relation based on its primary key and functional dependencies between its attributes.
Often executed as a series of steps. Each step corresponds to a specific normal form, which has known properties.
As normalization proceeds, relations become progressively more restricted (stronger) in format and also less vulnerable to update anomalies.
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16. Unnormalized Form (UNF)
A table that contains one or more repeating groups.
Note: A repeating group is an attribute or group of attributes within a table that occurs with multiple values for a single occurrence of the nominated key attributes for that table. For example a book with multiple authors, etc
To create an unnormalized table:
transform data from information source (e.g. form) into table format with columns and rows.
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17. First normal form (1NF)
A table is in First Normal Form (1NF) iff all its attributes are atomic.
A domain is atomic if its elements are considered to be indivisible units. A relation in which intersection of each row and column contains one and only one value.
Implies that it should have no composite attributes or multi-valued attributes.
In case a table is not in 1NF, we do two things
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18. UNF to 1NF First identify a primary key, then Either
Place each value of a repeating group on a tuple with duplicate values of the non-repeating data (called “flattening” the table) Or
Make a new table to cater for multi-valued attributes.
Place repeating data along with copy of the original key attribute(s) into a separate relation
The new primary key should be a combination of the (multi-valued) attribute and the primary key of the parent table.
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19. UNF to 1NF
Normalization

20. UNF to 1NF
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21. UNF to 1NF
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22. HEALTH HISTORY REPORT PET ID PET NAME PET TYPE PET AGE OWNER
VISIT DATE
PROCEDURE
PID
PNAME
246
ROVER
DOG 12
SAM COOK
JAN 13/2002 01
RABIES VACCINATION
MAR 27/2002 10
EXAMINE and TREAT WOUND
APR 02/2002 05
HEART WORM TEST
298
SPOT 2
TERRY KIM
JAN 21/2002 08
TETANUS VACCINATION
MAR 10/2002
341
MORRIS
CAT 4
JAN 23/2001
519
TWEEDY
BIRD
APR 30/2002 20
ANNUAL CHECK UP
EYE WASH
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23. Second Normal Form (2NF)
Based on concept of full functional dependency:
A and B are attributes of a relation,
B is fully dependent on A if B is functionally dependent on A but not on any proper subset of A.
2NF - A relation that is in 1NF and every non-primary-key attribute is fully functionally dependent on the primary key.
It applies to relations that have composite keys for a primary key.
Normalization
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24. 1NF to 2NF This involves the removal of partial dependencies
A partial dependency occurs when the primary key is made up of more than one attribute (i.e. it is a composite primary key) and there exists an attribute (which is a non-primary key attribute) that is dependant on only part of the primary key.
These partial dependencies can be removed by removing all of the partially dependent attributes into another relation along with a copy of the determinant attribute (which is part of the primary key in the original relation)
Normalization
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25. 1NF to 2NF
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27. Third Normal Form (3NF) Based on concept of transitive dependency:
A, B and C are attributes of a relation such that if A  B and B  C,
then C is transitively dependent on A through B. (Provided that A is not functionally dependent on B or C).
3NF - A relation that is in 1NF and 2NF and in which no non-primary-key attribute is transitively dependent on the primary key.
Normalization
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28. 2NF to 3NF Identify the primary key in the 2NF relation.
Identify functional dependencies in the relation.
If transitive dependencies exist on the primary key remove them by placing them in a new relation along with copy of their determinant.
Normalization
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31. Exercises: Instructions
The following tables are susceptible to update anomalies. Provide examples of insertion, deletion, and modification anomalies.
Describe and illustrate the process of normalizing the tables to 3NF. State any assumptions you make about the data shown in these tables.
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32. Exercise 1
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33. Exercise 2
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34. Exercise 3
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