Easy SQL Query | Beginner friendly ✅
\nselect product_id, "store1" as \'store\', store1 as \'price\'\nfrom products where store1 is not null\nunion\nselect product_id, "store2" as \'store\', store2
```\nselect product_id, "store1" as \'store\', store1 as \'price\'\nfrom products where store1 is not null\nunion\nselect product_id, "store2" as \'store\', store2 as \'price\'\nfrom products where store2 is not null\nunion\nselect product_id, "store3" as \'store\', store3 as \'price\'\nfrom products where store3 is not null\norder by product_id;\n```
['MySQL']