MySQL Solution
Code\n\n# Write your MySQL query statement below\nselect product_id, \'store1\' as store, store1 as price from Products\nwhere store1 is not null\nunion\nselect
# Code\n```\n# Write your MySQL query statement below\nselect product_id, \'store1\' as store, store1 as price from Products\nwhere store1 is not null\nunion\nselect product_id, \'store2\' as store, store2 as price from Products\nwhere store2 is not null\nunion\nselect product_id, \'store3\' as store, store3 as price from Products\nwhere store3 is not null;\n```
['MySQL']