<P> A table is a collection of related data held in a structured format within a database . It consists of columns, and rows . </P> <P> In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect . A table has a specified number of columns, but can have any number of rows . Each row is identified by one or more values appearing in a particular column subset . A specific choice of columns which uniquely identify rows is called the primary key . </P> <P> "Table" is another term for "relation"; although there is the difference in that a table is usually a multiset (bag) of rows where a relation is a set and does not allow duplicates . Besides the actual data rows, tables generally have associated with them some metadata, such as constraints on the table or on the values within particular columns . </P> <P> The data in a table does not have to be physically stored in the database . Views also function as relational tables, but their data are calculated at query time . External tables (in Informix or Oracle, for example) can also be thought of as views . </P>

In an access table each column contains a category of data called a(n)