Uploaded answers

.vscode/settings.json

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+{
+    "sqltools.connections": [
+        {
+            "previewLimit": 50,
+            "server": "localhost",
+            "port": 5432,
+            "askForPassword": true,
+            "driver": "PostgreSQL",
+            "username": "Hersh",
+            "name": "ShopifyDB",
+            "database": "ShopifyDB"
+        }
+    ]
+}

sql/task1.sql

@@ -1,14 +1,7 @@
--- Problem 1: Retrieve all products in the Sports category
+-- Problem 1: Retrieve all products in the Sports & Outdoors category
 -- Write an SQL query to retrieve all products in a specific category.
 
--- 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.
-
--- 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.
-
--- 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 P.product_id, P.product_name, P.description, P.price
+FROM Products AS P
+JOIN Categories AS C ON P.category_id = C.category_id
+WHERE C.category_name = 'Sports & Outdoors';

sql/task10.sql

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+-- 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.
+
+WITH ToysGamesProducts AS (
+    SELECT product_id
+    FROM Products
+    JOIN Categories ON Products.category_id = Categories.category_id
+    WHERE Categories.category_name = 'Toys & Games'
+), UserOrdersForToysGames AS (
+    SELECT Orders.user_id, Order_Items.product_id
+    FROM Orders
+    JOIN Order_Items ON Orders.order_id = Order_Items.order_id
+    WHERE Order_Items.product_id IN (SELECT product_id FROM ToysGamesProducts)
+    GROUP BY Orders.user_id, Order_Items.product_id
+), UserCount AS (
+    SELECT user_id, COUNT(*) AS product_count
+    FROM UserOrdersForToysGames
+    GROUP BY user_id
+    HAVING COUNT(*) = (SELECT COUNT(*) FROM ToysGamesProducts)
+)
+
+SELECT Users.user_id, Users.username
+FROM Users
+JOIN UserCount ON Users.user_id = UserCount.user_id;

sql/task11.sql

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+-- 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 RankedProducts AS (
+  SELECT
+    product_id,
+    product_name,
+    category_id,
+    price,
+    RANK() OVER (PARTITION BY category_id ORDER BY price DESC) AS price_rank
+  FROM
+    Products
+)
+
+SELECT
+  product_id,
+  product_name,
+  category_id,
+  price
+FROM
+  RankedProducts
+WHERE
+  price_rank = 1;

sql/task12.sql

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+-- 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 OrderedDates AS (
+  SELECT
+    user_id,
+    order_date,
+    LAG(order_date) OVER (PARTITION BY user_id ORDER BY order_date) AS prev_order_date,
+    LEAD(order_date) OVER (PARTITION BY user_id ORDER BY order_date) AS next_order_date
+  FROM
+    Orders
+),
+ConsecutiveOrders AS (
+  SELECT
+    user_id,
+    order_date,
+    CASE
+      WHEN order_date = prev_order_date + INTERVAL '1 day' OR
+           order_date = next_order_date - INTERVAL '1 day' THEN 1
+      ELSE 0
+    END AS is_consecutive
+  FROM
+    OrderedDates
+),
+ConsecutiveGroups AS (
+  SELECT
+    user_id,
+    SUM(is_consecutive) OVER (PARTITION BY user_id ORDER BY order_date ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS consecutive_days
+  FROM
+    ConsecutiveOrders
+)
+SELECT DISTINCT
+  U.user_id,
+  U.username
+FROM
+  Users U
+JOIN
+  ConsecutiveGroups CG ON U.user_id = CG.user_id
+WHERE
+  consecutive_days >= 2;

sql/task2.sql

@@ -1,19 +1,9 @@
--- Problem 5: Retrieve the products with the highest average rating
--- 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.
+-- 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.
 
--- 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.
-
--- 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.
-
--- 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.
+SELECT U.user_id, U.username, COUNT(O.order_id) AS total_orders
+FROM Users AS U
+LEFT JOIN Orders AS O ON U.user_id = O.user_id
+GROUP BY U.user_id, U.username
+ORDER BY U.user_id;

sql/task3.sql

@@ -1,19 +1,9 @@
--- Problem 9: Retrieve the top 3 categories with the highest total sales amount
--- 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.
+-- 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.
 
--- 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.
-
--- 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.
-
--- 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.
+SELECT P.product_id, P.product_name, AVG(R.rating) AS average_rating
+FROM Products AS P
+LEFT JOIN Reviews AS R ON P.product_id = R.product_id
+GROUP BY P.product_id, P.product_name
+ORDER BY P.product_id;

sql/task4.sql

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+-- 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_spent
+FROM Users AS U
+JOIN Orders AS O ON U.user_id = O.user_id
+GROUP BY U.user_id, U.username
+ORDER BY total_spent DESC
+LIMIT 5;

sql/task5.sql

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+-- Problem 5: Retrieve the products with the highest average rating
+-- 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 ProductRatings AS (
+  SELECT
+    P.product_id,
+    P.product_name,
+    AVG(R.rating) AS average_rating
+  FROM Products AS P
+  LEFT JOIN Reviews AS R ON P.product_id = R.product_id
+  GROUP BY P.product_id, P.product_name
+)
+
+SELECT product_id, product_name, average_rating
+FROM ProductRatings
+WHERE average_rating = (
+  SELECT MAX(average_rating)
+  FROM ProductRatings
+);

sql/task6.sql

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+-- 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
+JOIN 
+    Orders O ON U.user_id = O.user_id
+JOIN 
+    Order_Items OI ON O.order_id = OI.order_id
+JOIN 
+    Products P ON OI.product_id = P.product_id
+GROUP BY 
+    U.user_id, U.username
+HAVING 
+    COUNT(DISTINCT P.category_id) = (SELECT COUNT(*) FROM Categories);

sql/task7.sql

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+-- 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.review_id IS NULL;

sql/task8.sql

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+-- 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.
+
+WITH OrderedUsers AS (
+  SELECT
+    U.user_id,
+    U.username,
+    O.order_date,
+    LAG(O.order_date) OVER (PARTITION BY U.user_id ORDER BY O.order_date) AS prev_order_date
+  FROM
+    Orders O
+    JOIN Users U ON O.user_id = U.user_id
+)
+
+SELECT DISTINCT
+  user_id,
+  username
+FROM
+  OrderedUsers
+WHERE
+  order_date = DATE_ADD(prev_order_date, INTERVAL 1 DAY);

sql/task9.sql

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+-- Problem 9: Retrieve the top 3 categories with the highest total sales amount
+-- 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.
+
+SELECT
+    C.category_id,
+    C.category_name,
+    SUM(OI.quantity * OI.unit_price) AS total_sales_amount
+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
+ORDER BY
+    total_sales_amount DESC
+LIMIT 3;