日期和字符串互相转换，

日期和字符串互相转换，

 1.日期与字符串的转换

select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual;   -- //日期转化为字符串

select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss') from dual -- //字符串转化为日期

select to_char( to_date(300,'J'),'Jsp') from dual                       -- //转换为英文

 

2.求某天是星期几

select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day') from dual;      
   星期一      

select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;      
   monday

 

 

3.两个日期间的天数

select floor(sysdate - to_date('20100612','yyyymmdd')) from dual;

 

 

4.Oracle-subStr函数

select max(to_number(subStr(businesscode,3))) from agententity