oracle中的数据怎么让他在指定时间内自动销毁？

使用job 或者 schedule_job定时调用procedures根据删除条件删除即可。

设置Repeat Interval
Job 和Schedule 中REPEAT_INTERVAL 参数都是用来控制执行的频率或周期，虽然说周期是一个时间性概念，不过REPEAT_INTERVAL 指定的时候并不是一个时间值，而是由一组关键字描述的时间。
除了前面介绍Job 和Schedule 的REPEAT_INTERVAL 参数时，提到该参数拥有FREQ 以及INTERVAL 两个关键字，其实除此之外，还有如BYMONTH、BYWEEKNO、BYYEARDAY、BYDATE 等等参数，可以用来进行更精确的定义，比如通过BYMONTH 关键字指定调度运行的月份，BYDAY 指定调度在哪天运行等等。

REPEAT_INTERVAL 参数的详细语法如下：
repeat_interval = regular_schedule | combined_schedule
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
regular_schedule = frequency_clause
[";" interval_clause] [";" bymonth_clause] [";" byweekno_clause]
[";" byyearday_clause] [";" bydate_clause] [";" bymonthday_clause]
[";" byday_clause] [";" byhour_clause] [";" byminute_clause]
[";" bysecond_clause] [";" bysetpos_clause] [";" include_clause]
[";" exclude_clause] [";" intersect_clause][";" periods_clause]
[";" byperiod_clause]
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
combined_schedule = schedule_list [";" include_clause]
[";" exclude_clause] [";" intersect_clause]
frequency_clause = "FREQ" "=" ( predefined_frequency | user_defined_frequency )
predefined_frequency = "YEARLY" | "MONTHLY" | "WEEKLY" | "DAILY" |
"HOURLY" | "MINUTELY" | "SECONDLY"
user_defined_frequency = named_schedule
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
interval_clause = "INTERVAL" "=" intervalnum
intervalnum = 1 through 99
bymonth_clause = "BYMONTH" "=" monthlist
monthlist = monthday ( "," monthday)*
month = numeric_month | char_month
numeric_month = 1 | 2 | 3 ... 12
char_month = "JAN" | "FEB" | "MAR" | "APR" | "MAY" | "JUN" |
"JUL" | "AUG" | "SEP" | "OCT" | "NOV" | "DEC"
byweekno_clause = "BYWEEKNO" "=" weeknumber_list
weeknumber_list = weeknumber ( "," weeknumber)*
weeknumber = [minus] weekno
weekno = 1 through 53
byyearday_clause = "BYYEARDAY" "=" yearday_list
yearday_list = yearday ( "," yearday)*
yearday = [minus] yeardaynum
yeardaynum = 1 through 366
bydate_clause = "BYDATE" "=" date_list
date_list = date ( "," date)*
date = [YYYY]MMDD [ offset | span ]
bymonthday_clause = "BYMONTHDAY" "=" monthday_list
monthday_list = monthday ( "," monthday)*
monthday = [minus] monthdaynum
monthdaynum = 1 through 31
byday_clause = "BYDAY" "=" byday_list
byday_list = byday ( "," byday)*
byday = [weekdaynum] day
weekdaynum = [minus] daynum
daynum = 1 through 53 /* if frequency is yearly */
daynum = 1 through 5 /* if frequency is monthly */
day = "MON" | "TUE" | "WED" | "THU" | "FRI" | "SAT" | "SUN"
byhour_clause = "BYHOUR" "=" hour_list
hour_list = hour ( "," hour)*
hour = 0 through 23
byminute_clause = "BYMINUTE" "=" minute_list
minute_list = minute ( "," minute)*
minute = 0 through 59
bysecond_clause = "BYSECOND" "=" second_list
second_list = second ( "," second)*
second = 0 through 59
bysetpos_clause = "BYSETPOS" "=" setpos_list
setpos_list = setpos ("," setpos)*
setpos = [minus] setpos_num
setpos_num = 1 through 9999
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
include_clause = "INCLUDE" "=" schedule_list
exclude_clause = "EXCLUDE" "=" schedule_list
intersect_clause = "INTERSECT" "=" schedule_list
schedule_list = schedule_clause ("," schedule_clause)*
schedule_clause = named_schedule [ offset ]
named_schedule = [schema "."] schedule
periods_clause = "PERIODS" "=" periodnum
byperiod_clause = "BYPERIOD" "=" period_list
period_list = periodnum ("," periodnum)*
periodnum = 1 through 100
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
offset = ("+" | "-") ["OFFSET:"] duration_val
span = ("+" | "-" | "^") "SPAN:" duration_val
duration_val = dur-weeks | dur_days
dur_weeks = numofweeks "W"
dur_days = numofdays "D"
numofweeks = 1 through 53
numofdays = 1 through 376
minus = "-"
这个语法形式看起来复杂无比，其实实用起来很简单，之所以看起来复杂，是因为其功能太过灵活。

例如：设置任务仅在周5 的时候运行：
REPEAT_INTERVAL => 'FREQ=DAILY; BYDAY=FRI';
REPEAT_INTERVAL => 'FREQ=WEEKLY; BYDAY=FRI';
REPEAT_INTERVAL => 'FREQ=YEARLY; BYDAY=FRI';
上述三条语句虽然指定的关键字小有差异，不过功能相同。
设置任务隔一周运行一次，并且仅在周5 运行：
REPEAT_INTERVAL => 'FREQ=WEEKLY; INTERVAL=2; BYDAY=FRI';
设置任务在当月最后一天运行：
REPEAT_INTERVAL => 'FREQ=MONTHLY; BYMONTHDAY=-1';
设置任务在3 月10 日运行：
REPEAT_INTERVAL => 'FREQ=YEARLY; BYMONTH=MAR; BYMONTHDAY=10';
REPEAT_INTERVAL => 'FREQ=YEARLY; BYDATE=0310';
上述两条语句功能相同。
设置任务每10 隔天运行：
REPEAT_INTERVAL => 'FREQ=DAILY; INTERVAL=10';
设置任务在每天的下午4、5、6 点时运行：
REPEAT_INTERVAL => 'FREQ=DAILY; BYHOUR=16,17,18';
设置任务在每月29 日运行：
REPEAT_INTERVAL => 'FREQ=MONTHLY; BYMONTHDAY=29';
设置任务在每年的最后一个周5 运行：
REPEAT_INTERVAL => 'FREQ=YEARLY; BYDAY=-1FRI';
设置任务每隔50 个小时运行：
REPEAT_INTERVAL => 'FREQ=HOURLY; INTERVAL=50';
另外，你是否在怀念常规job 中设置interval 的简便，虽然功能较弱，但是设置操作非常简单，无须懊恼，
其实SCHEDULER 中的REPEAT_INTERVAL 也完全可以按照那种方式设置，前面都说了，REPEAT_INTERVAL
实际上是指定周期，直接指定一个时间值，当然也是周期喽。
比如说，设置任务每天执行一次，也可以设置REPEAT_INTERVAL 参数值如下：
REPEAT_INTERVAL => 'trunc(sysdate)+1'
又比如设置任务每周执行一次：
REPEAT_INTERVAL => 'trunc(sysdate)+7'、

不过需要注意，这种方式仅用于创建SCHEDULER 中jobs 时使用，不能用于schedule。