text: -- 1) Show all information about customers who do not have cars.
  SELECT cus.id,cus.name,cus.phone,cus.city FROM customer cus LEFT JOIN customer_cars cc ON  cus.id = cc.customer_id WHERE cc.customer_id IS NULL;
  
  -- 2) Show all customer information and the total amount spent most money.
  SELECT cus.id,cus.name,cus.phone,cus.city,SUM(c.price) FROM customer cus 
  JOIN customer_cars cc ON cus.id = cc.customer_id 
  JOIN cars c ON c.id = cc.cars_id 
  GROUP BY cus.id  ORDER BY 4 DESC LIMIT 1; 
  
  -- 3) Show “Customer Name”, “Phone”, “City”, “Car Models”, “Production Name”, “Total
  -- Cost” of the client who bought the most Japanese cars.
  SELECT cus.name,cus.phone,cus.city,GROUP_CONCAT(c.model),GROUP_CONCAT(DISTINCT m.name),SUM(c.price) FROM customer cus 
  JOIN customer_cars cc ON cc.customer_id = cus.id 
  JOIN cars c ON cc.cars_id = c.id 
  JOIN manufacture m ON c.manufc_id = m.id 
  WHERE m.country = "Japan" GROUP BY cus.id LIMIT 1;
  
  -- 4) Show all information about manufacture and a list of car models that sold more
  -- cars.
  SELECT m.id,m.name,m.country,m.city,GROUP_CONCAT(DISTINCT c.model) FROM manufacture m 
  JOIN cars c ON c.manufc_id = m.id 
  JOIN customer_cars cc ON c.id = cc.cars_id 
  GROUP BY m.id ORDER BY COUNT(*) DESC LIMIT 1;