Suppose you need to fire a trigger based on the change of value of a column and then perform some action based on it. You can do it easily like the below.
CREATE OR REPLACE TRIGGER TEST_TRIGGER
after UPDATE of COLUMNName ON TABLENAME1
for each row
NEW.COLUMNName= ‘0’ and NEW.COLUMNName2=’1′
if :new.COLUMNName= ‘0’ and :new.COLUMNName2=’1′ then
update tablename2 set columname3= ‘2’;