Use the EXPRESSION parameter after a column name to set that column to the value returned by a SQL operator or specially written PL/SQL function. The operator or function is indicated in a SQL string that follows the EXPRESSION parameter. Any arbitrary expression may be used in this context provided that any parameters required for the operator or function are correctly specified and that the result returned by the operator or function is compatible with the data type of the column being loaded.
The combination of column name, EXPRESSION parameter, and a SQL string is a complete field specification:
column_name EXPRESSION "SQL string"
In both conventional path mode and direct path mode, the EXPRESSION parameter can be used to load the default value into column_name:
column_name EXPRESSION "DEFAULT"
Note that if DEFAULT is used and the mode is direct path, then use of a sequence as a default will not work.