How can I set columns for an entire table in one UPDATE based on the SUM of a join table column? I have tables  companies and employees:

 explain companies;
+--------------------+---------------+------+-----+---------+----------------+
| Field              | Type          | Null | Key | Default | Extra          |
+--------------------+---------------+------+-----+---------+----------------+
| id                 | int(11)       | NO   | PRI | NULL    | auto_increment |
| score              | int(11)       | NO   | MUL | NULL    |                |
+--------------------+---------------+------+-----+---------+----------------+


 explain employees;
+--------------------+---------------+------+-----+---------+----------------+
| Field              | Type          | Null | Key | Default | Extra          |
+--------------------+---------------+------+-----+---------+----------------+
| id                 | int(11)       | NO   | PRI | NULL    | auto_increment |
| company_id         | int(11)       | NO   | PRI | NULL    |                |
| score              | int(11)       | NO   | MUL | NULL    |                |
+--------------------+---------------+------+-----+---------+----------------+


What I'd like to do is update the companies.score column based on the SUM of the employees.score column where employees.company_id = companies.id.

So given Company A and Company B, and Employee A1 (score 5), Employee A2 (score 2), and Employee B1 (score 3); I want to update Company A's score to 7, and Company B's score to 3.

What's the most elegant way to achieve this in MySQL?

Thanks!
update companies c set c.score = (select sum(e.score) from employees e where e.company_id = c.id);