to_char（sysdate,'D'）的用法

select to_char(sysdate,'D') from dual;   这周的第几天；Day of week (1–7) 1,2,3,4,5,6,7－－注意：每星期的第1天是”星期日“

select to_char(sysdate,'DD') from dual;这个月的第几天；Day of month (1–31) 1,2,3,4…31

select to_char(sysdate,'DDD') from dual;今年的第几天；Day of year (1–366) 1,2,3,4…366