Do you think that it is possible to represent the five rules of
normalization in a single rule?
Well, here it is:
"Store each data item with its determinant as the
identifier in a record/table."
By data item I mean any data element consisting of a domain of values
(which are surrogates of things in the real world), which are members of a
population called by the name of the data item/element.
Determinant is based on a relationship between two populations. If the members of one, say Y, are
functionally dependent on the other, say X, then we say that X determines
Y. The functional dependency can be
expressed as Y = Fn(X). For example, if
we had department as one population and employees as another, and we assume
that an employee can work in at most one department (at a time), then there is
a functional relationship between them:
Dept = Fn(Employee), that is, given a member of the employee population
(ID) that determines a unique value for Dept, hence a function. If there cannot be a Y without an X, then we
have a functional dependency.
In a side note, the relationship could involve a single population, in
which case we call it a reflexive relationship.
An example would be "is boss of" on an employee population.
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