DAYOFMONTH(date) returns the day of the month for date, in the range 0 to 31. : DAYOFMONTH « Date Time Functions « MySQL Tutorial

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

DAY() is a synonym for DAYOFMONTH().

mysql>
mysql> SELECT DAYOFMONTH('1998-02-03');
+--------------------------+
| DAYOFMONTH('1998-02-03') |
+--------------------------+
|                        3 |
+--------------------------+
1 row in set (0.00 sec)

mysql>