Editing Relational model (section)

=== Database normalization ===
{{Main|Database normalization}}
[[Relation (database)|Relation]]s are classified based upon the types of anomalies to which they're vulnerable. A database that is in the [[first normal form]] is vulnerable to all types of anomalies, while a database that is in the domain/key normal form has no modification anomalies. Normal forms are hierarchical in nature. That is, the lowest level is the first normal form, and the database cannot meet the requirements for higher level normal forms without first having met all the requirements of the lesser normal forms.<ref name="Normalization">David M. Kroenke, ''Database Processing: Fundamentals, Design, and Implementation'' (1997), Prentice-Hall, Inc., pages 130–144</ref>