Aggiungere una somma in una join

[optime]

no compriendo la tortuosità del ragionamento

SELECT 
   R.article_id, 
   A.article_title,
   SUM(R.article_hits)
FROM 
   articoli AS A INNER JOIN visite AS R ON A.article_id = R.article_id
GROUP BY 
   R.article_id,
   A.article_title
ORDER BY 
   SUM(R.article_hits) DESC
LIMIT 
   0,5

facce sape'