Rearrange Products Table.sql

SELECT product_id,
       'store1' AS store,
       store1 AS price
  FROM Products
 WHERE store1 IS NOT NULL

 UNION

 SELECT product_id,
       'store2' AS store,
       store2 AS price
  FROM Products
 WHERE store2 IS NOT NULL

 UNION

 SELECT product_id,
       'store3' AS store,
       store3 AS price
  FROM Products
 WHERE store3 IS NOT NULL

 ORDER BY product_id, store;