WHEN Condition

The WHEN condition makes the triggered action dependent on the outcome of a test. When you include a WHEN condition in a triggered action, the statements in the triggered action list execute only if the condition evaluates to true. If the WHEN condition evaluates to false or unknown, then the statements in the triggered action list are not executed.

If the triggered action is in a FOR EACH ROW section, its condition is evaluated for each row. For example, the triggered action in the following trigger executes only if the condition in the WHEN clause is true: 
CREATE TRIGGER up_price
   UPDATE OF unit_price ON stock
   REFERENCING OLD AS pre NEW AS post
   FOR EACH ROW WHEN(post.unit_price > pre.unit_price * 2)
   (INSERT INTO warn_tab VALUES(pre.stock_num, pre.order_num, 
      pre.unit_price, post.unit_price, CURRENT));

An SPL routine that executes inside the WHEN condition carries the same restrictions as a UDR that is called in a data manipulation statement. That is, the SPL routine cannot contain certain SQL statements. For information on which statements are restricted, see Restrictions on SPL Routines in Data-Manipulation Statements.