oracle extract()函数

select extract(year from sysdate) as year ,
extract(month from sysdate) as month,
extract(day from sysdate) as day
 from dual;  //使用extract()函数，分别取出年月日

      YEAR      MONTH        DAY
---------- ---------- ----------
      2020         10         26

select extract(day from d2 - d1) from (
       select to_timestamp('2020-5-15 5:00:00','yyyy-mm-dd hh24:mi:ss') d2,
              to_timestamp('1985-5-15 5:00:00','yyyy-mm-dd hh24:mi:ss') d1 from dual);//计算d2倒d1相差多少天

EXTRACT(DAYFROMD2-D1)
---------------------
                12784