# Normalization usually involves dividing a database
into two or more tables and defining relationships between the tables.
# 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 via the defined relationships.
**There
are three main normal forms, each with increasing levels of normalization:
· First Normal Form (1NF): Each field in
a table contains different information. For example, in an employee list, each
table would contain only one birthdate field.
· Second Normal Form (2NF): Each field
in a table that is not a determiner of the contents of another field must
itself be a function of the other fields in the table.
· Third Normal Form (3NF): No duplicate
information is permitted. So, for example, if two tables both require a
birthdate field, the birthdate information would be separated into a separate
table, and the two other tables would then access the birthdate information via
an index
field in the birthdate table. Any change to a birthdate would automatically be
reflect in all tables that link to the birthdate table.
There
are additional normalization levels, such as Boyce Codd Normal Form (BCNF),
fourth normal form (4NF) and fifth normal form (5NF). While
normalization makes databases more efficient to maintain, they can also make
them more complex because data is separated into so many different tables.
(2) In data processing, a process applied to all data in
a set that produces a specific statistical property. For example, each
expenditure for a month can be divided by the total of all expenditures to
produce a percentage.
(3) In programming,
changing the format of a floating-point number so the left-most digit in
the mantissa is not a zero.
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