<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> <P> In terms of the relational model of databases, a table can be considered a convenient representation of a relation, but the two are not strictly equivalent . For instance, an SQL table can potentially contain duplicate rows, whereas a true relation cannot contain duplicate tuples . Similarly, representation as a table implies a particular ordering to the rows and columns, whereas a relation is explicitly unordered . However, the database system does not guarantee any ordering of the rows unless an ORDER BY clause is specified in the SELECT statement that queries the table . </P>

Each table in a database is made up of rows called fields