例如2016/10/17 10:17:22 加5分钟，然后转成字符串呢？
select to_char(sysdate+5/1440,'yyyy-mm-dd hh24:mi:ss') as timechar from dual
http://www.orafaq.com/faq/how_does_one_add_a_day_hour_minute_second_to_a_date_value
当前时间减去7分钟的时间
select sysdate,sysdate - interval '7' MINUTE from dual;
http://blog.csdn.net/cherayliu/article/details/8085843/
http://www.2cto.com/database/201604/501997.html
http://www.cnblogs.com/xiao-yu/archive/2011/05/24/2055967.html