Week 6 Normalization

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 Normalization is a data analysis technique to
design a database system.
 It allows the database designer to understand the
current data structures in an organization.
 Furthermore, it aids any future changes and
enhancements to the system.
 Normalization is a technique for producing
relational schema with the following properties:
 No Information Redundancy
 No Update Anomalies
 The end result of Normalization is a set of entities,
which removes unnecessary redundancy (ie
duplication of data) and avoids the anomalies which
The Process of Normalization
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 Process involves applying a series of tests on a
relation to determine whether it satisfies or violates
the requirements of a given normal form.
 When a test fails, the relation is decomposed into
simpler relations that individually meet the
Normalization tests.
 The higher the normal form the less vulnerable to
update anomalies the relations become.
 Three Normal forms: 1NF, 2NF and 3NF were
initially proposed by Codd.
 All these normal forms are based on the functional
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Normalization
Stages

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Normalization
Stages

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Normalization
Stages
https://youtu.be/ygfikznRjpw

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Transform a table of unnormalised data
into first normal form (1NF) any repeating
attributes to a new table.
The process is as follows:
 Identify repeating attributes.
 Remove these repeating attributes to a
new table together with a copy of the key
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The First Normal Form -
1NF

The First Normal Form -
1NF
https://youtu.be/K7vzLrGCV50

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Class Exercises
Normalize to the 1st Form

The Second Normal Form -
2NF
https://youtu.be/9L10Q1nAfyg

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 Transform 1NF data into second normal form (2NF).
 Remove any -key attributes (partial Dependencies) that only
depend on part of the table key to a new table.
 What has to be determined "is field A dependent upon field B or
vice versa?" This means: "Given a value for A, do we then have
only one possible value for B, and vice versa?" If the answer is
yes, A and B should be put into a new relation with A becoming
the primary key. A should be left in the original relation and
marked as a foreign key.
 Ignore tables with (a) a simple key or (b) with no non-key
attributes (these go straight to 2NF with no conversion).
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Normalization 2NF

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 Take each non-key attribute in turn and ask the question: is
this attribute dependent on one part of the key?
 If yes, remove the attribute to a new table with a copy of
the part of the key it is dependent upon. The key it is
dependent upon becomes the key in the new table. Underline
the key in this new table.
 If no, check against other part of the key and repeat above
process
 If still no, ie: not dependent on either part of the key, keep
attribute in current table.
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Normalization 2NF

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 The first table went straight to 2NF as it has a simple key
(Project Code).
 Employee name, Department No and Department Name
are dependent upon Employee No only. Therefore, they
were moved to a new table with Employee No being the
key.
 However, Hourly Rate is dependent upon both Project
Code and Employee No as an employee may have a
different hourly rate depending upon which project they
are working on.
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Normalization 2NF

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Normalization
Example
Once you identify a table’s purpose, then look at each of
the table’s columns and ask yourself, “Does this column
serve to describe what the primary key identifies?”
If you answer “yes,” then the column is dependent on
the primary key and belongs in the table.
If you answer “no,” then the column should be moved
different table.

Normalization to the 3NF
https://youtu.be/_K7fcFQowy8

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If a non-key attribute is more dependent on another non-
key attribute than the table key:
 Move the dependent attribute, together with a copy of
the non-key attribute upon which it is dependent, to a
new table.
 Make the non-key attribute, upon which it is dependent,
the key in the new table. Underline the key in this new
table.
 Leave the non-key attribute, upon which it is dependent,
in the original table and mark it a foreign key (*).
 The project team table went straight from 2NF to 3NF as
it only has one non-key attribute.
 Department Name is more dependent upon Department
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Normalization
Example

Each table cell should contain a single value.
Each record needs to be unique.

 Rule 1- Be in 1NF
 Rule 2- Single Column Primary Key

 Rule 1- Be in 2NF
 Rule 2- Has no transitive functional dependencies

Week 6 Normalization

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Week 6 Normalization