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Posted by David Kerber on 04/12/07 20:14
In article <461e877b$0$328$e4fe514c@news.xs4all.nl>,
usenet@No.Spam.Please.invalid says...
> sqlservernewbie@yahoo.com wrote:
> > Hi Everyone,
> >
> >
> > Here is a theoretical, and definition question for you.
> >
> >
> > In databases, we have:
> >
> >
> > Relation
> > a table with columns and rows
> >
> >
> > Attribute
> > a named column/field of a relation
> >
> >
> > Domain
> > a set of allowable values for one or more attributes
> >
> > Tuple
> > a row of a relation
> >
> >
> > Degree
> > the number of attributes a relation contains
> > Number of fields in a table
> >
> >
> > Cardinality
> > the number of tuples/rows a relation contains
> >
> >
> >
> >
> > But!
> >
> > What is the definition for the number of unique values in a field?
> >
> > So, if you have 100 rows in a table, and the field is
> > the gender field, with only values of: M, F.
> > The result is 2 unique values.
> >
> >
> > What do we call this concept?
> > "the number of unique values in a column?"
> >
> > Is there one?
> >
> >
> > Thanks a lot!
>
> (Column) Cardinality = number of distinct column/attribute values.
> Table Cardinality = number of rows in a table.
Shouldn't that be *distinct* (non-duplicate) rows in the table?
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