select sysdate,sysdate+numtosinterval(1,'second') from dual;    加1秒

select sysdate,sysdate-numtosinterval(1,'second') from dual;    减1秒

select sysdate,sysdate+numtosinterval(45,'minute') from dual;    加45分钟

select sysdate,sysdate+numtosinterval(1,'hour') from dual;    加1个小时