foreign key
(redirected from Foreign key constraint)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.
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.
foreign key
In relational databases, it is a field in one table that is indexed in another. Foreign keys provide the building blocks for relating tables. For example, in a customer order table, the salesperson field might contain an employee number. That field would be a foreign key in the table, because the employee table would be indexed on employee number. See entity relationship model. |
| Foreign Keys |
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| Note the "FK" indications in this Erwin entity relationship modeling program. Every foreign key is a field in one table that is indexed in another. (Example courtesy of Logic Works, Inc.) |