Rearrange Products Table solution and explanation

def rearrange_products(products):
    result = []
    stores = ['store1', 'store2', 'store3']
    for product in products:
        product_id = product['product_id']
        for store in stores:
            if product[store] is not None:
                result.append({'product_id': product_id, 'store': store, 'price': product[store]})
    return result

# Example usage
products = [{'product_id': 0, 'store1': 95, 'store2': 100, 'store3': 105}, {'product_id': 1, 'store1': 70, 'store2': None, 'store3': 80}]
print(rearrange_products(products))

using System;
using System.Collections.Generic;

class Program {
    public static List<Dictionary<string, object>> RearrangeProducts(List<Dictionary<string, object>> products) {
        var result = new List<Dictionary<string, object>>();
        var stores = new List<string> { "store1", "store2", "store3" };
        foreach (var product in products) {
            foreach (var store in stores) {
                if (product[store] != null) {
                    result.Add(new Dictionary<string, object> {
                        { "product_id", product["product_id"] },
                        { "store", store },
                        { "price", product[store] }
                    });
                }
            }
        }
        return result;
    }

    static void Main() {
        var products = new List<Dictionary<string, object>> {
            new Dictionary<string, object> { { "product_id", 0 }, { "store1", 95 }, { "store2", 100 }, { "store3", 105 } },
            new Dictionary<string, object> { { "product_id", 1 }, { "store1", 70 }, { "store2", null }, { "store3", 80 } }
        };
        var result = RearrangeProducts(products);
        foreach (var row in result) {
            Console.WriteLine($"{{product_id: {row["product_id"]}, store: {row["store"]}, price: {row["price"]}}}");
        }
    }
}

function rearrangeProducts(products) {
    let result = [];
    products.forEach(product => {
        const productId = product['product_id'];
        ['store1', 'store2', 'store3'].forEach(store => {
            if (product[store] !== null) {
                result.push({product_id: productId, store: store, price: product[store]});
            }
        });
    });
    return result;
}

// Example usage
const products = [
    { product_id: 0, store1: 95, store2: 100, store3: 105 },
    { product_id: 1, store1: 70, store2: null, store3: 80 }
];
console.log(rearrangeProducts(products));

#include <stdio.h>
#include <stdlib.h>

void rearrangeProducts(int products[][4], int num_products) {
    for (int i = 0; i < num_products; i++) {
        int productId = products[i][0];
        for (int store = 1; store <= 3; store++) {
            if (products[i][store] != -1) { // Assuming -1 as a placeholder for NULL
                printf("Product ID: %d, Store: store%d, Price: %d\n", productId, store, products[i][store]);
            }
        }
    }
}

int main() {
    int products[2][4] = {
        {0, 95, 100, 105},
        {1, 70, -1, 80}
    };
    rearrangeProducts(products, 2);
    return 0;
}

# Write your MySQL query statement below
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;