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