What is Normalization ?
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Answer Posted / gopal sharma
In the field of relational database design, normalization is a systematic way of ensuring that a database structure is suitable for general-purpose querying and free of certain undesirable characteristics—insertion, update, and deletion anomalies—that could lead to a loss of data integrity.[1]
Database normalization is a technique for designing
relational database tables to minimize duplication of
information and, in so doing, to safeguard the database
against certain types of logical or structural problems,
namely data anomalies.
For example, when multiple instances of a given piece of
information occur in a table, the possibility exists that
these instances will not be kept consistent when the data
within the table is updated, leading to a loss of data
integrity. A table that is sufficiently normalized is less
vulnerable to problems of this kind, because its structure
reflects the basic assumptions for when multiple instances
of the same information should be represented by a single
instance only.
The formal classifications describing the level of database
normalization in a data model are called Normal Forms (NF)
and the process of doing this is Normalization.
First normal form :
• A table is in first normal form when it contains no
repeating groups.
• The repeating column or fields in an un normalized table
are removed from the table and put in to tables of their own.
• Such a table becomes dependent on the parent table from
which it is derived.
• The key to this table is called concatenated key, with the
key of the parent table forming a part it.
Second normal form:
• A table is in second normal form if all its non_key fields
fully dependent on the whole key.
• This means that each field in a table ,must depend on the
entire key.
• Those that do not depend upon the combination key, are
moved to another table on whose key they depend on.
• Structures which do not contain combination keys are
automatically in second normal form.
Third normal form:
• A table is said to be in third normal form , if all the
non key fields of the table are independent of all other non
key fields of the same table.
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