CREATE OR REPLACE TRIGGER tri_vreserve
AFTER UPDATE OF vreserve14 ON pm_pa_payapply
DECLARE
  myexp exception
BEGIN
  IF old.vreserve14 != '' AND new.vreserve14 == '' THEN
    RAISE myexp;
  END IF;
  EXCEPTION_INIT
    WHEN myexp THEN raise_application_error('-20002','vreserve14字段的值被设置为空')；
oracle查询表是否有触发器
select trigger_name from all_triggers where table_name='PM_PA_PAYAPPLY'; 
通过触发器名，获取触发器的具体内容
select text from all_source where type='TRIGGER' AND name='TRI_VRESERVE';
注意触发器名要大写。