Understanding Mode (Optional Parameter , value 0 to 7)
The week can start on Sunday or Monday,
To understand uses of MODE, read WEEK() function
If mode is not given, then it is considered as 0. The default_week_format of the MySQL system variables is not considered in YEARWEEK() function like WEEK() function. This is the main difference while using MODE between WEEK() function and YEARWEEK() function.