15일차 # 5-29: Sequential Control: GOTO and NULL Statements

참고 : http://docs.oracle.com/cd/B19306_01/appdev.102/b14261/controlstructures.htm#sthref976

  * NULL Statement:

You can use the NULL statement to indicate that you are aware of a possibility, 

but no action is necessary.

EXCEPTION

 WHEN ZERO_DIVIDE THEN

   ROLLBACK;

 WHEN OTHERS THEN

   NULL;

END;

  * 문제) 아래 블럭은 에러가 발생한다. 해결 방법은?

DECLARE

 done  BOOLEAN;

BEGIN

 FOR i IN 1..50 LOOP

   IF done THEN

     GOTO end_loop;

   END IF;

 <<end_loop>> -- not allowed unless an executable statement follows

 END LOOP; -- raises an error without the previous NULL

END;

/

↓ ↓ ↓ 

DECLARE

 done  BOOLEAN;

BEGIN

 FOR i IN 1..50 LOOP

   IF done THEN

     GOTO end_loop;

   END IF;

 <<end_loop>> -- not allowed unless an executable statement follows

 NULL; -- add NULL statement to make label legal and fix the error

 END LOOP; -- raises an error without the previous NULL

END;

/