context-var            A context variable. A temporary name that
                           you associate with a relation. You define
                           a context variable in a relation clause.
                           For more information see the entry on
                           Context Variables.

    field-name             The name of a field in a relation. For
                           example, once you have defined E as
                           the context variable for the EMPLOYEES
                           relation, E.LAST_NAME is a value
                           expression that refers to a value from
                           the LAST_NAME field of EMPLOYEES.