修改日期格式为年月日时分秒: alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual; //日期转化为年月日时分秒格式
select to_char(sysdate,'yyyy') nowYear from dual; //获取时间的年
select to_char(sysdate,'mm') nowMonth from dual; //获取时间的月
select to_char(sysdate,'dd') nowDay from dual; //获取时间的日
select to_char(sysdate,'hh24') nowHour from dual; //获取时间的时
select to_char(sysdate,'mi') nowMinute from dual; //获取时间的分
select to_char(sysdate,'ss') nowSecond from dual; //获取时间的秒
原文链接：https://blog.csdn.net/seekandfindyou/article/details/80668980