g., a dorm) when inserting information about a first entity (e.g., a student), or losing
information about a second entity (e.g., a dorm) when an entity of a different type is deleted (e.g., the last student
in the dorm). Normalization is the process of subjecting relations to tests. Passing the tests will insure that the
relation will show desirable properties.
The goal of normalization is to insure that each relation represents a single theme. For instance, a relation
should have information about students, and a relation should have information about dorms, but a relation that
has information about both students and dorms will lead to trouble.
CHAP. 8] DATABASE 145
There are various normal ???forms??? which have been identified for relational databases. Higher levels of
normalization lead to designs that reduce data redundancy and avoid the update anomalies mentioned above.
Any higher normal form also conforms to all lower normal forms. Thus, a relation in third normal form (3NF)
is also in second normal form (2NF), and first normal form (1NF).
Discussions of normal forms rely upon the concept of functional dependency. When the value of one attribute,
or set of attributes, determines the value of another attribute, a functional dependency exists, and the first attribute,
or set of attributes, is called the determinant.
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