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