Simple MySQL solution
\nSelect product_id,"store1" store, store1 as price from Products where store1 is not NULL\nunion\nSelect product_id,"store2" store, store2 as price from Produc
```\nSelect product_id,"store1" store, store1 as price from Products where store1 is not NULL\nunion\nSelect product_id,"store2" store, store2 as price from Products where store2 is not NULL \nunion\nSelect product_id,"store3" store, store3 as price from Products where store3 is not NULL\n\n```\n\n**Please UpVote if it was Helpful :)**
['MySQL']