DATE_FORMAT(date,format)

%U  Week (00..53), where Sunday is the first day of the week; WEEK() mode 0
%u  Week (00..53), where Monday is the first day of the week; WEEK() mode 1
%V  Week (01..53), where Sunday is the first day of the week; WEEK() mode 2; used with %X
%v  Week (01..53), where Monday is the first day of the week; WEEK() mode 3; used with %x
%W  Weekday name (Sunday..Saturday)
%w  Day of the week (0=Sunday..6=Saturday)
%X  Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
%x  Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v

0   Sunday  0-53    with a Sunday in this year
1   Monday  0-53    with 4 or more days this year
2   Sunday  1-53    with a Sunday in this year
3   Monday  1-53    with 4 or more days this year
4   Sunday  0-53    with 4 or more days this year
5   Monday  0-53    with a Monday in this year
6   Sunday  1-53    with 4 or more days this year
7   Monday  1-53    with a Monday in this year

mysql> SELECT WEEK('2008-02-20');
        -> 7
mysql> SELECT WEEK('2008-02-20',0);
        -> 7
mysql> SELECT WEEK('2008-02-20',1);
        -> 8
mysql> SELECT WEEK('2008-12-31',1);
        -> 53

来源: https://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_week