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