--得到系统当前时间
SELECT SYSDATE FROM DUAL
SELECT TO_CHAR(SYSDATE,'YYYY-MM-DD HH24:MM:SS') FROM DUAL --2011-10-19 09:10:24 。24小时
SELECT TO_CHAR(SYSDATE,'YYYY-MM-DD HH:MM:SS') FROM DUAL --2011-10-19 09:10:24 。12小时
SELECT TO_CHAR(SYSDATE,'YYYY-MM-DD HH/MM/SS') FROM DUAL --2011-10-19 09/10/00
SELECT TO_CHAR(SYSDATE,'YYYY') FROM DUAL --2011
SELECT TO_CHAR(SYSDATE,'MM') FROM DUAL --10
SELECT TO_CHAR(SYSDATE,'DD') FROM DUAL -- 19
SELECT TO_CHAR(SYSDATE,'WWW') FROM DUAL --423
SELECT TO_CHAR(SYSDATE,'DDD') FROM DUAL --292