What is normalization and its forms?
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Answer Posted / rohit
Database normalization, sometimes referred to as canonical
synthesis, 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.
Higher degrees of normalization typically involve more
tables and create the need for a larger number of joins,
which can reduce performance. Accordingly, more highly
normalized tables are typically used in database
applications involving many isolated transactions (e.g. an
automated teller machine), while less normalized tables tend
to be used in database applications that need to map complex
relationships between data entities and data attributes
(e.g. a reporting application, or a full-text search
application).
Database theory describes a table's degree of normalization
in terms of normal forms of successively higher degrees of
strictness. A table in third normal form (3NF), for example,
is consequently in second normal form (2NF) as well; but the
reverse is not necessarily the case.
Although the normal forms are often defined informally in
terms of the characteristics of tables, rigorous definitions
of the normal forms are concerned with the characteristics
of mathematical constructs known as relations. Whenever
information is represented relationally, it is meaningful to
consider the extent to which the representation is normalized.
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