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Research Note Topic:
Research Note Description:
process of databases refers to the step-by-step decomposition of complex records into simple records. Normalization reduces redundancy using the principle of non-loss decomposition. Non-loss decomposition is the reduction of a table to smaller tables without the loss of information.
Very often the process of normalization follows the process of drawing E/R diagrams. However, depending on how detailed and precise the E/R diagram is, the process of normalization may not at all be necessary. The tables derived from the E/R diagram may already be normalized. Infact, they will be, atleast in the first normal form, as we will soon see.
Normalization reduces redundancy.
is the unnecessary repetition of data. It causes problems with storage and retrieval of data.
Types of Normal Forms
Normalization results in the formation of tables that satisfy certain specified constraints, and represent certain normal forms. Normal forms are table structures with minimum redundancy.
Several normal forms have been identified. The most important and widely used of these are the:
First Normal Form (1 NF),
Second Normal Form (2 NF),
Third Normal Form (3 NF), and
Boyce-Codd Normal Form (BCNF)
The first, second, and third normal forms were originally defined by Dr. E. F. Codd. Later, Boyce and Codd introduced normal form called the Boyce-Codd Normal Form (BCNF).
First Normal Form (1 NF):
Here, one needs to set the very basic rules for an organized database by:
eliminating duplicative columns from the same table; and
creating separate tables for each group of related data, and identifying each row with a unique column or set of columns
(the primary key)
Second Normal Form (2 NF):
Data in the table's rows in 1 NF may be redundant. The table should, therefore, be further decomposed without any loss of information.
A table is in 2 NF when it is in 1NF, and further addresses the concept of removing duplicative data by:
removing subsets of data that apply to multiple rows of a table, and place them in separate tables; and
creating relationships between these new tables and their predecessors through the use of foreign keys.
Third Normal Form (3 NF):
A table is said to be in 3 NF when it is in 2 NF,and another major step is performed by:
removing columns that are not dependent upon the primary key.
Boyce-Codd Normal Form (BCNF):
A table in Boyce-Codd Normal Form is almost the same as 3 NF, except that now we need to introduce new tables (all in 3 NF) for the removed columns so that there is no information-loss.
Prof. Ashay Dharwadker