10일 20일 30일 1 1 2 dbms_pipe.receive_me 1 3 OR 1 4 PG_SLEEP20 2 5 SLEEP20 6 WAITFOR 4 7 dbms_pipe.receive_messagea20 1 1 2 WAITFOR 1 3 dbms_pipe.receive_me 1 4 OR 5 SLEEP20 6 PG_SLEEP20 7 dbms_pipe.receive_messagea20 1 1 2 WAITFOR 2 3 dbms_pipe.receive_me 1 4 OR 2 5 SLEEP20 6 PG_SLEEP20 3 7 dbms_pipe.receive_messagea20 11위 - 20위