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The Normal Forms 3NF And BCNF

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The Normal Forms 3NF And BCNF
The Normal Forms
3NF and BCNF
Yunliang Jiang

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Normalization
Solution: Normal Forms
Introducing 3NF and BCNF
3NF
Examples
BCNF

Normalization
• Normalization is the process of efficiently organizing data in a database with two goals in mind
• First goal: eliminate redundant data
– for example, storing the same data in more than one table

• Second Goal: ensure data dependencies make sense – for example, only storing related data in a table

Benefits of Normalization







Less storage space
Quicker updates
Less data inconsistency
Clearer data relationships
Easier to add data
Flexible Structure

The Solution: Normal Forms
• Bad database designs results in:
– redundancy: inefficient storage.
– anomalies: data inconsistency, difficulties in maintenance • 1NF, 2NF, 3NF, BCNF are some of the early forms in the list that address this problem

Third Normal Form (3NF)
1) Meet all the requirements of the 1NF

2) Meet all the requirements of the 2NF
3) Remove columns that are not dependent upon the primary key.

1) First normal form -1NF
• 1NF : if all attribute values are atomic: no repeating group, no composite attributes
– Really easy to achieve

• The following table is not in 1NF
DPT_NO

MG_NO

EMP_NO

EMP_NM

D101

12345

20000
20001
20002

Carl Sagan
Mag James
Larry Bird

D102

13456

30000
30001

Jim Carter
Paul Simon

Table in 1NF
DPT_NO

MG_NO

EMP_NO

EMP_NM

D101

12345

20000

Carl Sagan

D101

12345

20001

Mag James

D101

12345

20002

Larry Bird

D102

13456

30000

Jim Carter

D102

13456

Paul Simon
30001

• all attribute values are atomic because there are no repeating group and no composite attributes.

2) Second Normal Form
• 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

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