2025-08-15 12:38:40 +0000 UTC

(
    SELECT 
        product_id,
        'store1' AS store,
        store1 AS price
    FROM 
        Products
    WHERE 
        store1 IS NOT NULL
) UNION (
    SELECT 
        product_id,
        'store2' AS store,
        store2 AS price
    FROM 
        Products
    WHERE 
        store2 IS NOT NULL
) UNION (
    SELECT 
        product_id,
       'store3' AS store,
       store3 AS price
    FROM 
        Products
    WHERE 
        store3 IS NOT NULL
)
ORDER BY 
    product_id, 
    store;