title: CASE statement to do nothing
body: <p>I have a trigger with a case statement. In the last section of the code in the ELSE block, i want the trigger to not do anything and exit if the values do not match in the previous CASE statements. How do i do this:</p>
  
  <pre><code>create or replace TRIGGER  "CONVEYANCE_REQUEST_T3"  
  BEFORE  
  insert or update on "CONVEYANCE_REQUEST"  
  for each row  
  begin  
  
  CASE   
   when :NEW.REGULAR_TRAVEL_MODE = '2 WHEELER' THEN  
   BEGIN  
       CASE  
           when :NEW.WAY_TYPE = 'ONE WAY' THEN   
                SELECT RATE_PER_KM * (SELECT DISTANCE_ONEWAY  FROM     DISTANCE_MASTER WHERE PROJECT_CODE = :NEW.PROJECT_CODE ) * 1 INTO     :NEW.REGULAR_AMOUNT FROM CONVEYANCE_RATE WHERE TRAVEL_MODE = :NEW.REGULAR_TRAVEL_MODE;  
           WHEN :NEW.WAY_TYPE ='TWO WAY' THEN  
                SELECT RATE_PER_KM * (SELECT DISTANCE_ONEWAY FROM DISTANCE_MASTER WHERE PROJECT_CODE = :NEW.PROJECT_CODE ) * 2 INTO :NEW.REGULAR_AMOUNT FROM CONVEYANCE_RATE WHERE TRAVEL_MODE = :NEW.REGULAR_TRAVEL_MODE;  
       END CASE;  
   END;  
   when :NEW.REGULAR_TRAVEL_MODE = '4 WHEELER' THEN  
   BEGIN  
       CASE  
          when :NEW.WAY_TYPE = 'ONE WAY' THEN   
                SELECT RATE_PER_KM * (SELECT DISTANCE_ONEWAY   FROM DISTANCE_MASTER WHERE PROJECT_CODE = :NEW.PROJECT_CODE ) * 1 INTO :NEW.REGULAR_AMOUNT FROM CONVEYANCE_RATE WHERE TRAVEL_MODE = :NEW.REGULAR_TRAVEL_MODE;  
           WHEN :NEW.WAY_TYPE ='TWO WAY' THEN  
                SELECT RATE_PER_KM * (SELECT DISTANCE_ONEWAY  FROM DISTANCE_MASTER WHERE PROJECT_CODE = :NEW.PROJECT_CODE ) * 2 INTO :NEW.REGULAR_AMOUNT FROM CONVEYANCE_RATE WHERE TRAVEL_MODE = :NEW.REGULAR_TRAVEL_MODE;  
       END CASE;  
   END;
   ELSE 
    ****statement to just exit &amp; not do anything*****
  
   END CASE;  
  END;  
  </code></pre>