Rules of Data Normalization


Rules of Data Normalization

1NF - Make a separate table for each set of related attributes, and give each table a
primary key.
2NF - If an attribute depends on only part of a multi-valued key, remove it to a
separate table.
3NF - 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 - No table may contain two or more 1:n or n:m relationships that are not directly
related.

5NF - There may be practical constrains on information that justify separating
logically related many-to-many relationships.
DKNF Domain-Key Normal Form - a model free from all modification
anomalies.
Note:
All normal forms are additive, in that if a model is in 3rd normal form, it is by
definition also in 2nd and 1st.

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