EXTRACT() 函数

--EXTRACT() 函数用于提取日期/时间的单独部分，比如年、月、日、小时、分钟等等。  select sysdate,        extract(year from sysdate),        extract(month from sysdate),        extract(day from sysdate)   from dual s;       SELECT EXTRACT(HOUR FROM TIMESTAMP '2010-01-10 11:12:13'),        EXTRACT(minute FROM TIMESTAMP '2010-01-10 11:12:13'),        EXTRACT(second FROM TIMESTAMP '2010-01-10 11:12:13')   FROM DUAL;