15일차 # 8-21: Exception Propagation

참고 : http://docs.oracle.com/cd/B19306_01/appdev.102/b14261/errors.htm#i3365

  * To reraise an exception, use a RAISE statement without an exception name

  * An exception raised in a declaration propagates immediately to the enclosing block.

  * An exception raised inside a handler propagates immediately to the enclosing block.