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