Re-entrant triggers

A re-entrant trigger refers to a case in which the triggered action can reference the triggering table. In other words, both the triggering event and the triggered action can operate on the same table. For example, suppose the following UPDATE statement represents the triggering event:

UPDATE tab1 SET (col_a, col_b) = (col_a + 1, col_b + 1);

The following triggered action is legal because column col_c is not a column that the triggering event has updated:

UPDATE tab1 SET (col_c) = (col_c + 3);

In the preceding example, a triggered action on col_a or col_b would be illegal because a triggered action cannot be an UPDATE statement that references a column that was updated by the triggering event.

Important: Select triggers cannot be re-entrant triggers. If the triggering event is a SELECT statement, the triggered action cannot operate on the same table.

For a list of the rules that describe those situations in which a trigger can and cannot be re-entrant, see the CREATE TRIGGER statement in the HCL OneDB™ Guide to SQL: Syntax.