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