The SQL Set Operators UNION, INTERSECT, and MINUS can be used if the underlying RDBMS supports it, in the following places:
•In the SQL Command Dialog.
•In USoft Batch, except when used in an external set that has a child set.
•In the SqlScript() method.
•UNION ALL can also be used as the main statement of a logical view.
•All Set Operators can be used in logical views and in constraints as long as they are not used in the topmost select statement.
Furthermore, in the USoft Remote Rules Service API, the UNION operator is supported.
NOTE: If SQL Set Operators UNION, INTERSECT, and MINUS are used in constraints, note that they cannot be used:
•As the main statement.
•In the FROM-clause of the main query, in the case of a logical view that contains a UNION ALL.
•As the manipulated table, in the case of a logical view that contains a UNION ALL
This basically means that set operators are only allowed in sub-selects in constraints.