Beginner-Friendly Solution Using MySQL || Clear
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```mysql []\n# Write your MySQL query statement below\nselect product_id, \'store1\' as store, store1 as price\nfrom Products\nwhere store1 is not null\nunion\nselect product_id, \'store2\' as store, store2 as price\nfrom Products\nwhere store2 is not null\nunion\nselect product_id, \'store3\' as store, store3 as price\nfrom Products\nwhere store3 is not null\n```
['MySQL']