Database Normalization,1NF,2NF,3NF – Overview

Database normalization is the process of organizing the fields and tables of a relational database to minimize redundancy and dependency. Normalization usually involves dividing large tables into smaller (and less redundant) tables and defining relationships between them. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database using the defined relationships.

First normal form (1NF) is a property of a relation in a relational database. A relation is in first normal form if the domain of each attribute contains only atomic values, and the value of each attribute contains only a single value from that domain.

Second normal form (2NF) : a table is in 2NF if and only if it is in 1NF and no non-prime attribute is dependent on any proper subset of any candidate key of the table. A non-prime attribute of a table is an attribute that is not a part of any candidate key of the table.

Third normal form (3NF) : a table is in 3NF if and only if both of the following conditions hold:

The relation R (table) is in second normal form (2NF)
Every non-prime attribute of R is non-transitively dependent (i.e. directly dependent) on every superkey of R.

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