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