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