Thanks Samuel,
At first this looked similar to a sub-query which is supported by PervasiveSQL and which I use often. However, Pervasive only allows sub-queries as part of the WHERE clause and they must have Select statements in the innermost query. Moreover, Pervasive doesn't support OLD TABLE, NEW TABLE or FINAL TABLE or the OUTPUT command of SQL.

This and other limitations have led me to decide to move to another database which will probably be MySQL.