mysql：

//字串轉日期
select str_to_date('09/01/2009','%m/%d/%Y') from dual;

select str_to_date('20140422154706','%Y%m%d%H%i%s') from dual;

select str_to_date('2014-04-22 15:47:06','%Y-%m-%d %H:%i:%s') from dual;

//日期轉字串
select date_format('2014-04-22 15:47:06','%Y-%m-%d %H:%i:%s') from dual;

oracle：

//日期轉字串
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual;   

select to_char(sysdate,'yyyy') as nowYear   from dual;   //獲取時間的年  

select to_char(sysdate,'mm')    as nowMonth from dual;   //獲取時間的月  

select to_char(sysdate,'dd')    as nowDay   from dual;   //獲取時間的日  

select to_char(sysdate,'hh24') as nowHour   from dual;   //獲取時間的時  

select to_char(sysdate,'mi')   as nowMinute from dual;   //獲取時間的分  

select to_char(sysdate,'ss')   as nowSecond from dual;   //獲取時間的秒

//字串轉日期
select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss') from dual;