Try this:
Syntax:
Select Table1.Field1, Table1.Field2, Table1.Field3
from Table1 LEFT JOIN Table2 ON (Table1.Field1 = Table2.Field1) And
(Table1.Field2 = Table2.Field2) WHERE (((Table2.Field1) is Null))
Union
Select Table2.Field1, Table2.Field2, Table2.Field3
from Table1 RIGHT JOIN Table2 ON...