CREATE PROCEDURE EveryFifthModel()
BEGIN

SET @id=0;
SELECT @id:=@id+1 AS currow,model,TYPE, IFNULL(pr1,0)+IFNULL(pr2,0)+IFNULL(pr4,0) AS avgprice FROM
(SELECT vp_product.TYPE,vp_product.model,AVG(vp_printer.price) AS pr1, AVG(vp_pc.price) AS pr2,
 AVG(vp_laptop.price) AS pr4 FROM vp_product LEFT JOIN vp_printer USING(model)
 LEFT JOIN vp_laptop USING(model) LEFT JOIN vp_pc USING(model) GROUP BY model) AS xx GROUP BY model HAVING NOT avgprice=0 AND currow % 5 = 1 ORDER BY model ASC ;

END;