oracle日期时间的加减法

加法  select sysdate,add_months(sysdate,12) from dual;        --加1年 select sysdate,add_months(sysdate,1) from dual;        --加1月 select sysdate,to_char(sysdate+7,'yyyy-mm-dd HH24:MI:SS') from dual;   --加1星期 select sysdate,to_char(sysdate+1,'yyyy-mm-dd HH24:MI:SS') from dual;   --加1天 select sysdate,to_char(sysdate+1/24,'yyyy-mm-dd HH24:MI:SS') from dual;  --加1小时 select sysdate,to_char(sysdate+1/24/60,'yyyy-mm-dd HH24:MI:SS') from dual;  --加1分钟 select sysdate,to_char(sysdate+1/24/60/60,'yyyy-mm-dd HH24:MI:SS') from dual;  --加1秒减法 select sysdate,add_months(sysdate,-12) from dual;        --减1年 select sysdate,add_months(sysdate,-1) from dual;        --减1月 select sysdate,to_char(sysdate-7,'yyyy-mm-dd HH24:MI:SS') from dual;   --减1星期 select sysdate,to_char(sysdate-1,'yyyy-mm-dd HH24:MI:SS') from dual;   --减1天 select sysdate,to_char(sysdate-1/24,'yyyy-mm-dd HH24:MI:SS') from dual;  --减1小时 select sysdate,to_char(sysdate-1/24/60,'yyyy-mm-dd HH24:MI:SS') from dual;  --减1分钟 select sysdate,to_char(sysdate-1/24/60/60,'yyyy-mm-dd HH24:MI:SS') from dual;  --减1秒