   WEEK(date[,mode])
The function returns the week number for date.  The two-argument form
of WEEK() allows you to specify whether the week starts on Sunday or
Monday and whether the return value should be in the range from 0 to
53 or from 1 to 53. If the mode argument is
omitted, the value of the default_week_format system variable is
used (or 0 before MySQL 4.0.14).
See also : [Server system variables].

The following table describes how the mode argument works:

     	 First day 	 	
   Mode 	 of week 	 Range 	 Week 1 is the first week...
   0 	 Sunday 	 0-53 	 with a Sunday in this year
   1 	 Monday 	 0-53 	 with more than 3 days this year
   2 	 Sunday 	 1-53 	 with a Sunday in this year
   3 	 Monday 	 1-53 	 with more than 3 days this year
   4 	 Sunday 	 0-53 	 with more than 3 days this year
   5 	 Monday 	 0-53 	 with a Monday in this year
   6 	 Sunday 	 1-53 	 with more than 3 days this year
   7 	 Monday 	 1-53 	 with a Monday in this year
  

A mode value of 3 can be used as of MySQL 4.0.5.
Values of 4 and above can be used as of MySQL 4.0.17.
