查询oracle24小时内切换频率

 column dt format  a10
 column dy format a7
 column Total format 999
 column h0  format 99
 column h1  format 99
 column h2  format 99
 column h3  format 99
 column h4  format 99
 column h5  format 99
 column h6  format 99
 column h7  format 99
 column h8  format 99
 column h9  format 99
 column h10  format 99
 column h11  format 99
 column h12  format 99
 column h13  format 99
 column h14  format 99
 column h15  format 99
 column h16  format 99
 column h17  format 99
 column h18  format 99
 column h19  format 99
 column h20  format 99
 column h21  format 99
 column h22  format 99
 column h23  format 99

 SELECT  to_char(first_time,'yyyy-mm-dd') Dt,
         to_char(first_time, 'Dy') dy,
         count(1) "Total",
         SUM(decode(to_char(first_time, 'hh24'),'00',1,0)) "h0",
         SUM(decode(to_char(first_time, 'hh24'),'01',1,0)) "h1",
         SUM(decode(to_char(first_time, 'hh24'),'02',1,0)) "h2",
         SUM(decode(to_char(first_time, 'hh24'),'03',1,0)) "h3",
         SUM(decode(to_char(first_time, 'hh24'),'04',1,0)) "h4",
         SUM(decode(to_char(first_time, 'hh24'),'05',1,0)) "h5",
         SUM(decode(to_char(first_time, 'hh24'),'06',1,0)) "h6",
         SUM(decode(to_char(first_time, 'hh24'),'07',1,0)) "h7",
         SUM(decode(to_char(first_time, 'hh24'),'08',1,0)) "h8",
         SUM(decode(to_char(first_time, 'hh24'),'09',1,0)) "h9",
         SUM(decode(to_char(first_time, 'hh24'),'10',1,0)) "h10",
         SUM(decode(to_char(first_time, 'hh24'),'11',1,0)) "h11",
         SUM(decode(to_char(first_time, 'hh24'),'12',1,0)) "h12",
         SUM(decode(to_char(first_time, 'hh24'),'13',1,0)) "h13",
         SUM(decode(to_char(first_time, 'hh24'),'14',1,0)) "h14",
         SUM(decode(to_char(first_time, 'hh24'),'15',1,0)) "h15",
         SUM(decode(to_char(first_time, 'hh24'),'16',1,0)) "h16",
         SUM(decode(to_char(first_time, 'hh24'),'17',1,0)) "h17",
         SUM(decode(to_char(first_time, 'hh24'),'18',1,0)) "h18",
         SUM(decode(to_char(first_time, 'hh24'),'19',1,0)) "h19",
         SUM(decode(to_char(first_time, 'hh24'),'20',1,0)) "h20",
         SUM(decode(to_char(first_time, 'hh24'),'21',1,0)) "h21",
         SUM(decode(to_char(first_time, 'hh24'),'22',1,0)) "h22",
         SUM(decode(to_char(first_time, 'hh24'),'23',1,0)) "h23"
 FROM    V$log_history
 group by to_char(first_time,'yyyy-mm-dd') ,
         to_char(first_time, 'Dy')
 Order by 1;

本文来自iDB Stock:http://www.idb-stock.net/idb/2011/05/24/134.html