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Database Normalization

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.

1NF - Eliminate Repeating Groups - Make a separate table for
each set of related attributes, and give each table a
primary key.

2NF - Eliminate Redundant Data - If an attribute depends on
only part of a multi-valued key, remove it to a separate table.

3NF - Eliminate Columns Not Dependent On Key - If attributes
do not contribute to a description of the key, remove them
to a separate table.

BCNF - Boyce-Codd Normal Form - If there are non-trivial
dependencies between candidate key attributes, separate them
out into distinct tables.

4NF - Isolate Independent Multiple Relationships - No table
may contain two or more 1:n or n:m relationships that are
not directly related.

5NF - Isolate Semantically Related Multiple Relationships -
There may be practical constrains on information that
justify separating logically related many-to-many relationships.
ONF Optimal Normal Form - a model limited to only simple
(elemental) facts, as expressed in Object Role Model notation.
DKNF Domain-Key Normal Form - a model free from all
modification anomalies.

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