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Posted by Larry Coon on 04/12/07 18:31
sqlservernewbie@yahoo.com wrote:
> 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?
Using your definitions, it'd probably be "the cardinality of the
domain."
Larry Coon
University of California
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