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