mysql> SELECT count(wizard.id), team.name FROM wizard
    -> INNER JOIN player ON wizard.id=player.wizard_id
    -> INNER JOIN team ON player.team_id=team.id
    -> GROUP BY team.name
    -> GROUP BY count(wizard.id) DESC;
+------------------+------------+
| count(wizard.id) | name       |
+------------------+------------+
|               36 | Gryffindor |
|               21 | Slytherin  |
|               15 | Ravenclaw  |
|               12 | Hufflepuff |
+------------------+------------+
4 rows in set (0.00 sec)

mysql> SELECT COUNT(wizard.id), team.name FROM wizard
    -> INNER JOIN player ON wizard.id=player.wizard_id
    -> INNER JOIN team ON player.team_id=team.id
    -> GROUP BY team.name
    -> HAVING COUNT(wizard.id) >13
    -> ORDER BY name ASC;
+------------------+------------+
| count(wizard.id) | name       |
+------------------+------------+
|               36 | Gryffindor |
|               15 | Ravenclaw  |
|               21 | Slytherin  |
+------------------+------------+
3 rows in set (0.00 sec)

mysql> SELECT DAYOFWEEK(enrollment_date), CONCAT(firstname, ' ', lastname) AS fullname from wizard
    -> JOIN player ON wizard.id=player.wizard_id
    -> JOIN team ON player.team_id=team.id
    -> WHERE DAYOFWEEK(enrollment_date)=2 AND name="Gryffindor"
    -> ORDER BY enrollment_date;
+----------------------------+----------------------+
| DAYOFWEEK(enrollment_date) | fullname             |
+----------------------------+----------------------+
|                          2 | George Weasley       |
|                          2 | Alice Longbottom     |
|                          2 | Cadogan              |
|                          2 | Godric Gryffindor    |
|                          2 | Sirius Black         |
|                          2 | Aberforth Dumbledore |
|                          2 | Augusta Longbottom   |
+----------------------------+----------------------+
7 rows in set (0.00 sec)