mysql> select DAYOFWEEK('1998-02-03'); -> 3
WEEKDAY(date) 返回date的星期索引(0=星期一,1=星期二, ……6= 星期天)。
mysql> select WEEKDAY('1997-10-04 22:23:00'); -> 5 mysql> select WEEKDAY('1997-11-05'); -> 2