Completed assesement

sql/task1.sql

@@ -1,14 +1,29 @@
 -- Problem 1: Retrieve all products in the Sports category
 -- Write an SQL query to retrieve all products in a specific category.
+SELECT p.product_id, p.product_name, p.price FROM Products p JOIN Categories c ON p.category_id = c.category_id WHERE c.category_name = 'Sports';   
 
 -- Problem 2: Retrieve the total number of orders for each user
 -- Write an SQL query to retrieve the total number of orders for each user.
 -- The result should include the user ID, username, and the total number of orders.
+SELECT u.user_id, u.username, COUNT(o.order_id) AS total_orders
+FROM Users u
+JOIN Orders o ON u.user_id = o.user_id
+GROUP BY u.user_id, u.username;
 
 -- Problem 3: Retrieve the average rating for each product
 -- Write an SQL query to retrieve the average rating for each product.
 -- The result should include the product ID, product name, and the average rating.
+SELECT p.product_id, p.product_name, AVG(r.rating) AS average_rating 
+FROM Products p
+JOIN Reviews r ON p.product_id = r.product_id
+GROUP BY p.product_id, p.product_name;
 
 -- Problem 4: Retrieve the top 5 users with the highest total amount spent on orders
 -- Write an SQL query to retrieve the top 5 users with the highest total amount spent on orders.
 -- The result should include the user ID, username, and the total amount spent.
+SELECT u.user_id, u.username, SUM(o.total_amount) AS total_amount_spent
+FROM Users u
+JOIN Orders o ON u.user_id = o.user_id
+GROUP BY u.user_id, u.username
+ORDER BY total_amount_spent DESC
+LIMIT 5;

sql/task2.sql

@@ -2,18 +2,55 @@
 -- Write an SQL query to retrieve the products with the highest average rating.
 -- The result should include the product ID, product name, and the average rating.
 -- Hint: You may need to use subqueries or common table expressions (CTEs) to solve this problem.
+WITH avg_rating AS (
+    SELECT product_id, AVG(rating) AS average_rating
+    FROM Reviews
+    GROUP BY product_id;
+)
+SELECT p.product_id, p.product_name, ar.average_rating
+FROM Products p
+JOIN avg_rating ar ON p.product_id = ar.product_id
+ORDER BY ar.average_rating DESC
+LIMIT 1;
 
 -- Problem 6: Retrieve the users who have made at least one order in each category
 -- Write an SQL query to retrieve the users who have made at least one order in each category.
 -- The result should include the user ID and username.
 -- Hint: You may need to use subqueries or joins to solve this problem.
+SELECT u.user_id, u.username
+FROM Users u
+WHERE NOT EXISTS (
+    SELECT c.category_id
+    FROM Categories c
+    WHERE NOT EXISTS (
+        SELECT o.order_id
+        FROM Orders o
+        JOIN Order_Items oi ON o.order_id = oi.order_id
+        JOIN Products p ON oi.product_id = p.product_id
+        WHERE o.user_id = u.user_id AND p.category_id = c.category_id
+    )
+);
+
 
 -- Problem 7: Retrieve the products that have not received any reviews
 -- Write an SQL query to retrieve the products that have not received any reviews.
 -- The result should include the product ID and product name.
 -- Hint: You may need to use subqueries or left joins to solve this problem.
+SELECT p.product_id, p.product_name
+FROM Products p
+LEFT JOIN Reviews r ON p.product_id = r.product_id
+WHERE r.product_id IS NULL;
 
 -- Problem 8: Retrieve the users who have made consecutive orders on consecutive days
 -- Write an SQL query to retrieve the users who have made consecutive orders on consecutive days.
 -- The result should include the user ID and username.
--- Hint: You may need to use subqueries or window functions to solve this problem.
+-- Hint: You may need to use subqueries or window functions to solve this problem.
+WITH ConsecutiveOrders AS (
+    SELECT user_id, order_date,
+           LAG(order_date) OVER (PARTITION BY user_id ORDER BY order_date) AS prev_order_date
+    FROM Orders
+)
+SELECT DISTINCT u.user_id, u.username
+FROM Users u
+JOIN ConsecutiveOrders co ON u.user_id = co.user_id
+WHERE DATEDIFF(co.order_date, co.prev_order_date) = 1;

sql/task3.sql

@@ -2,18 +2,67 @@
 -- Write an SQL query to retrieve the top 3 categories with the highest total sales amount.
 -- The result should include the category ID, category name, and the total sales amount.
 -- Hint: You may need to use subqueries, joins, and aggregate functions to solve this problem.
+WITH CategorySales AS (
+    SELECT c.category_id, c.category_name, SUM(oi.quantity * oi.unit_price) AS total_sales
+    FROM Categories c
+    JOIN Products p ON c.category_id = p.category_id
+    JOIN Order_Items oi ON p.product_id = oi.product_id
+    GROUP BY c.category_id, c.category_name
+)
+SELECT category_id, category_name, total_sales
+FROM CategorySales
+ORDER BY total_sales DESC
+LIMIT 3;
 
 -- Problem 10: Retrieve the users who have placed orders for all products in the Toys & Games
 -- Write an SQL query to retrieve the users who have placed orders for all products in the Toys & Games
 -- The result should include the user ID and username.
 -- Hint: You may need to use subqueries, joins, and aggregate functions to solve this problem.
+SELECT u.user_id, u.username
+FROM Users u
+WHERE NOT EXISTS (
+    SELECT p.product_id
+    FROM Products p
+    JOIN Categories c ON p.category_id = c.category_id
+    WHERE c.category_name = 'Toys & Games'
+    AND NOT EXISTS (
+        SELECT oi.order_id
+        FROM Orders o
+        JOIN Order_Items oi ON o.order_id = oi.order_id
+        WHERE o.user_id = u.user_id
+        AND oi.product_id = p.product_id
+    )
+);
 
 -- Problem 11: Retrieve the products that have the highest price within each category
 -- Write an SQL query to retrieve the products that have the highest price within each category.
 -- The result should include the product ID, product name, category ID, and price.
 -- Hint: You may need to use subqueries, joins, and window functions to solve this problem.
+WITH MaxPrices AS (
+    SELECT category_id, MAX(price) AS max_price
+    FROM Products
+    GROUP BY category_id
+)
+SELECT p.product_id, p.product_name, p.category_id, p.price
+FROM Products p
+JOIN MaxPrices mp ON p.category_id = mp.category_id AND p.price = mp.max_price;
 
 -- Problem 12: Retrieve the users who have placed orders on consecutive days for at least 3 days
 -- Write an SQL query to retrieve the users who have placed orders on consecutive days for at least 3 days.
 -- The result should include the user ID and username.
 -- Hint: You may need to use subqueries, joins, and window functions to solve this problem.
+WITH ConsecutiveOrders AS (
+    SELECT user_id, order_date,
+           LAG(order_date, 1) OVER (PARTITION BY user_id ORDER BY order_date) AS prev_order_date,
+           LAG(order_date, 2) OVER (PARTITION BY user_id ORDER BY order_date) AS prev_prev_order_date
+    FROM Orders
+),
+ConsecutiveDays AS (
+    SELECT user_id
+    FROM ConsecutiveOrders
+    WHERE DATEDIFF(order_date, prev_order_date) = 1
+    AND DATEDIFF(prev_order_date, prev_prev_order_date) = 1
+)
+SELECT DISTINCT u.user_id, u.username
+FROM Users u
+JOIN ConsecutiveDays cd ON u.user_id = cd.user_id;