CASE statement to do nothing
<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>