This document discusses normalization, which is the process of organizing data in a database to minimize redundancy and dependency. It defines normalization through various normal forms, including first normal form (1NF), second normal form (2NF), and third normal form (3NF). These normal forms help reduce data anomalies like insertion, deletion, and update anomalies that can occur when data is redundant or dependent on other data. The benefits of normalization include using less storage space, allowing for quicker updates, and reducing data inconsistencies.

1. Normalization
1. Definition
▪ The theory of relational databases includes some wisdom about what is
and what is not good database design. These notions are expressed in
terms of restrictions, each of which excludes certain undesirable properties
from database designs. These sets of restrictions are called normal forms.
And normalization is the name given to the process of creating a database
design that does not violate them.
▪ A logical design method:
-- which minimizes data redundancy and reduces design flaws.
• Consists of applying various “normal” forms to the database design.
• The normal forms break down large tables into smaller subsets.

2. Normalization
2. Data Redundancy or Duplication
▪ Department name and manager are duplicated for all employees in the
department.
If redundancy exists then this can cause problems during normal
database operations:
• When data is inserted the database the data must be duplicated where ever
redundant versions of that data exists.
• When data is updated, all redundant data must be simultaneously updated to
reflect that change.
Consequences of redundancy
•
•
•
•
Wasted space
Potential performance cost
Potential inconsistency
Inability to represent data

3. Normalization
3. Anomalies
Insertion anomalies
If a new employee is added to deptid 2, all the info about the department
(name & manager) has to be re-input.
A new department, say it, can be added only when there exists an
employee for the new department.
Deletion anomalies
If the last employee from a department is deleted, then details of that
department disappear from the database.
Update anomalies
If the sales manager of Jones is replaced by Smith, all the records for
employees in sales department must be modified.

4. Normalization
4. Benefits of Normalization
• Less storage space
• Quicker updates
• Less data inconsistency
• Clearer data relationships
• Easier to add data
• Flexible structure

5. Normal Form
1. First Normal Form - 1nf
• A relation is said to be in first normal form (1nf) if all attribute values are atomic:
no repeating group, no composite attributes, and primary key is identified.
Patient
#
Surgeon
#
Surgery date
Patient name
Patient addr
Surgeon name
Surgery
Drug admin
Side
Effects
1111
145
01-jan-95
John white
15 new st. New york, ny
Gallstones removal
Penicillin
Rash
1111
311
12-jun-95
John white
15 new st. New york, ny
Beth little
Michael diamon
d
Kidney stones removal
None
None
1234
243
05-apr-94
Mary jones
10 main st. Rye, ny
Charles field
Eye cataract removal
Tetracycline
Fever
1234
467
10-may-95
Mary jones
10 main st. Rye, ny
Patricia gold
Thrombosis removal
None
None
2345
189
08-jan-96
Charles brown
Dogwood lane harrison, ny
David rosen
Open heart surgery
Cephalosporin
None
4876
145
05-nov-95
Hal kane
55 boston post road, chester, cn
Beth little
Cholecystectomy
Demicillin
None
5123
145
10-may-95
Paul kosher
Blind brook mamaroneck, ny
Beth little
Gallstones removal
None
None
6845
243
05-apr-94
Ann hood
Hilton road larchmont, ny
Charles field
Eye cornea replacement
Tetracycline
Fever
6845
243
15-dec-84
Ann hood
Hilton road larchmont, ny
Charles field
Eye cataract removal
None
None
• All attribute values are atomic because there are no repeating group and no
composite attributes.

6. Normal Form
2. Second Normal Form - 2nf
Second normal form (2nf) further addresses the concept of removing duplicative data:
• A relation r is in 2nf if
(a) r is 1nf , and
(b) all non-prime attributes are fully dependent on the candidate keys.
Which is creating relationships between these new tables and their
predecessors through the use of foreign keys.
Partial dependency must be eliminated.
Break the composite primary key into two parts, each part representing a separate
table.
• A prime attribute appears in a candidate key.
• There is no partial dependency in 2nf.

7. Normal Form
3. Third Normal Form - 3nf
A relation is said to be in third normal form if there is no transitive functional
dependency between nonkey attributes.
• When one nonkey attribute can be determined with one or more nonkey attributes
there is said to be a transitive functional dependency.
The side effect column in the surgery table is determined by the drug administered.
• Side effect is transitively functionally dependent on drug so surgery is not 3nf.

8. Normal Form
4. Denormalization
Though normalization is performed to reduce or eliminate
insertion, deletion or update anomalies, a completely normalized database
may not be the most efficient or effective implementation.
“denormalization” is sometimes used to improve efficiency.
Usually driven by the need to improve query speed.
Query speed is improved at the expense of more complex or problematic
DML (data manipulation language) for updates, deletions and insertions.