In SQL statements, a referenced table can be a base table, a derived table, a queue table, or a view. The semantics of derived tables and views are identical.
A derived table is obtained from one or more other tables as the result of a subquery.
This option enables the FROM clause to specify a spool made up of selected data from an underlying table set. The derived table acts like a viewed table.
You can invoke a scalar UDF from any point in a derived table.