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