Select rows from a supertable with the ONLY keyword
Although a SELECT statement on a supertable returns rows
from both the supertable and its subtables, you cannot tell which
rows come from the supertable and which rows come from the subtables.
To limit the results of a query to the supertable only, you must include
the ONLY keyword in the SELECT statement. For example, the following
query returns rows in the person table only.