这个SQL的特点是模拟日历（Calendar）形式，显示每小时产生的redo log数量：

SELECT * FROM (SELECT A.* FROM (SELECT * FROM (SELECT TO_DATE(b.date_time, 'DD/MM/YYYY') dt,TO_CHAR(TO_DATE(b.date_time, 'DD/MM/YYYY'), 'DAY') DAY,"00", "01", "02", "03", "04", "05", "06", "07", "08", "09","10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", TOTALFROM (SELECT date_time,SUM(DECODE(HOUR,'00',1,NULL)) "00", SUM(DECODE(HOUR,'01',1,NULL)) "01", SUM(DECODE(HOUR,'02',1,NULL)) "02",SUM(DECODE(HOUR,'03',1,NULL)) "03", SUM(DECODE(HOUR,'04',1,NULL)) "04", SUM(DECODE(HOUR,'05',1,NULL)) "05",SUM(DECODE(HOUR,'06',1,NULL)) "06", SUM(DECODE(HOUR,'07',1,NULL)) "07", SUM(DECODE(HOUR,'08',1,NULL)) "08",SUM(DECODE(HOUR,'09',1,NULL)) "09", SUM(DECODE(HOUR,'10',1,NULL)) "10", SUM(DECODE(HOUR,'11',1,NULL)) "11",SUM(DECODE(HOUR,'12',1,NULL)) "12", SUM(DECODE(HOUR,'13',1,NULL)) "13", SUM(DECODE(HOUR,'14',1,NULL)) "14",SUM(DECODE(HOUR,'15',1,NULL)) "15", SUM(DECODE(HOUR,'16',1,NULL)) "16", SUM(DECODE(HOUR,'17',1,NULL)) "17",SUM(DECODE(HOUR,'18',1,NULL)) "18", SUM(DECODE(HOUR,'19',1,NULL)) "19", SUM(DECODE(HOUR,'20',1,NULL)) "20",SUM(DECODE(HOUR,'21',1,NULL)) "21", SUM(DECODE(HOUR,'22',1,NULL)) "22", SUM(DECODE(HOUR,'23',1,NULL)) "23",COUNT(*) TOTALFROM (SELECT TO_CHAR(first_time, 'DD/MM/YYYY') DATE_TIME,SUBSTR(TO_CHAR(first_time, 'DD/MM/YYYY HH24:MI:SS'),12,2) HOUR FROM V$LOG_HISTORY)GROUP BY date_time) b)) A) ORDER BY dt DESC;