SQL | Easy to Understand | UNION & SELECT | Simple
\nSELECT product_id,\n\t"store1" AS store,\n\tstore1 AS price \nFROM Products WHERE store1 IS NOT null\nUNION\nSELECT product_id,\n\t"store2" AS store,\n\tstore
```\nSELECT product_id,\n\t"store1" AS store,\n\tstore1 AS price \nFROM Products WHERE store1 IS NOT null\nUNION\nSELECT product_id,\n\t"store2" AS store,\n\tstore2 AS price \nFROM Products WHERE store2 IS NOT null\nUNION\nSELECT product_id,\n\t"store3" AS store,\n\tstore3 AS price \nFROM Products WHERE store3 IS NOT null;\n\n```\nPlease upvote if you found this useful :)
['Union Find', 'MySQL']