foreign key

from The Free On-line Dictionary of Computing (8 July 2008)

foreign key

   <database> A {column} in a database {table} containing values
   that are also found in some {primary key} column (of a
   different table).  By extension, any reference to entities of
   a different type.

   Some {RDBMSs} allow a column to be explicitly labelled as a
   foreign key and only allow values to be inserted if they
   already exist in the relevant primary key column.

   [Is it still a foreign key if the primary key is in a different
   column in the __same__ table?]

   (2005-01-14)