WEEK(date[,mode]) returns the week number for date : WEEK « Date Time Functions « MySQL Tutorial

1. MySQL Tutorial
2. Date Time Functions
3. WEEK

The mode specifies whether the week starts on Sunday or Monday.

If the mode argument is omitted, the value of the default_week_format system variable is used.

The mode could be 0 ,1 ,2 ,3 ,4 ,5 ,6 ,7

mysql>
mysql> SELECT WEEK('1998-02-20');
+--------------------+
| WEEK('1998-02-20') |
+--------------------+
|                  7 |
+--------------------+
1 row in set (0.00 sec)

mysql> SELECT WEEK('1998-02-20',0);
+----------------------+
| WEEK('1998-02-20',0) |
+----------------------+
|                    7 |
+----------------------+
1 row in set (0.00 sec)

mysql> SELECT WEEK('1998-02-20',1);
+----------------------+
| WEEK('1998-02-20',1) |
+----------------------+
|                    8 |
+----------------------+
1 row in set (0.00 sec)

mysql> SELECT WEEK('1998-12-31',1);
+----------------------+
| WEEK('1998-12-31',1) |
+----------------------+
|                   53 |
+----------------------+
1 row in set (0.02 sec)

mysql> SELECT WEEK('2000-01-01',2);
+----------------------+
| WEEK('2000-01-01',2) |
+----------------------+
|                   52 |
+----------------------+
1 row in set (0.00 sec)

mysql>