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