Subqueries in the FROM Clause of SELECT

Table expressions in the FROM clause of a SELECT statement can be the triggering event on a table that is referenced by an uncorrelated subquery. In the following example, the subquery that specifies a table expression is the triggering event for any enabled Select triggers that are defined on col1 of tab1:

SELECT vcol FROM (SELECT FIRST 5 col1 FROM tab1 ORDER BY col1 ) vtab(vcol);