[slt2021]

queries like these are best suited for window functions, although I am not sure Mysql supports it:

  SELECT article, dealer, price FROM (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY article ORDER BY price DESC) as rnk
    FROM   shop s1
  ) sub 
  WHERE sub.rnk=1
  ORDER BY article; 

this query will be a single pass over table without loops/joins