text: ELECT count(name) as NUM, title as CLASS
  FROM children
  INNER JOIN class ON (class.id = id_class)
  GROUP BY class.title;
  
  SELECT name, age, title
  FROM children
  INNER JOIN class ON (class.id = id_class)
  ORDER BY age, class.title;
  
  SELECT count(name) as num, age FROM children GROUP BY age ORDER BY name DESC Limit 3;