Duda con ORDER BY

[quimfv]

Código MySQL:

SELECT tl.usrID, 
             u.usuario, 
             Sum(IF(tl.score,1,0)) as aciertos, 
             Sum(IF(tl.score,0,1)) as errores 
      FROM triviaLog tl
        INNER JOIN usuarios u
            ON tl.usr_id = u.id  
GROUP BY tl.usr_id
ORDER BY Sum(IF(tl.score,1,0)) DESC;
 

Si?