DE Challenge

sql/task1.sql

@@ -1,14 +1,43 @@
 -- Problem 1: Retrieve all products in the Sports category
 -- Write an SQL query to retrieve all products in a specific category.
+select *
+from Products
+where category_id = (select category_id from Categories where category_name = 'Sports & Outdoors');
 
 -- 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.
+with stat as
+    (select user_id, count(order_id) as cnt
+    from Orders
+    group by user_id)
+select u.user_id, u.username, stat.cnt
+from Users u
+inner join stat
+on u.user_id = o.user_id;
 
 -- 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.
+with rating as 
+    (select product_id, AVG(rating) as rate
+    from Reviews
+    group by product_id)
+select p.product_id, p.product_name, r.rate
+from Products p
+inner join rating r
+on p.product_id=r.product_id;
 
 -- 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.
+with spent as
+    (select user_id, sum(total_amount) as amt
+    from Orders
+    group by user_id)
+select u.user_id, u.username, s.amt
+from Users u
+inner join spent s
+on u.user_id = s.user_id
+order by s.amt desc
+limit 5;

sql/task2.sql

@@ -2,18 +2,53 @@
 -- 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 rating as 
+    (select product_id, AVG(rating) as rate
+    from Reviews
+    group by product_id)
+select p.product_id, p.product_name, r.rate
+from Products p
+inner join rating r
+on p.product_id=r.product_id
+where r.rate = (select max(rate) from rating);
 
 -- 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
+inner join Orders o
+on u.user_id = o.user_id
+inner join Order_Items oi
+on o.order_id = oi.order_id
+inner join Products p
+on oi.product_id = p.product_id
+group by u.user_id
+having count(distinct p.category_id) = (select count(category_id) from Category)
+
+
 -- 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;
 
 -- 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 consec as
+    (select user_id, order_date,
+        LAG(order_date) over (partition by user_id order by order_date) as prev
+    from Orders)
+select distinct c.user_id, u.username
+from consec c
+inner join Users u 
+on c.user_id = u.user_id
+WHERE datediff(day, c.order_date, c.prev) = 1;

sql/task3.sql

@@ -2,18 +2,64 @@
 -- 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
+from Categories c
+inner join Products p 
+on c.category_id = p.category_id
+inner join Order_Items oi 
+on p.product_id = oi.product_id
+inner join Orders o
+on oi.order_id = o.order_id
+group by c.category_id, c.category_name
+order by total 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
+inner join Orders o 
+on u.user_id = o.user_id
+inner join Order_Items oi 
+on o.order_id = oi.order_id
+inner join Products p 
+on oi.product_id = p.product_id
+inner join Categories c 
+on p.category_id = c.category_id
+where c.category_name = 'Toys & Games'
+group by u.user_id
+having count(distinct oi.product_id) = (select count(*) 
+                                        from Products p
+                                        left join Categorues c
+                                        on p.category_id = c.category_id
+                                        where c.category_id = 'Toys & Games');
+
 
 -- 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 ranking as 
+    (select product_id, product_name, category_id, price, rank() over (partition by category_id order by price desc) as rank
+    from Products)
+select product_id, product_name, category_id, price
+from ranking 
+where rank = 1;
 
 -- 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 tmp as 
+    (select user_id,order_date,
+        LAG(order_date, 1) over (partition by user_id order by order_date) as prev,
+        LAG(order_date, 2) OVER (partition by user_id order by order_date) AS pprev
+    from Orders)
+select distinct u.user_id, u.username
+from Users u
+left join tmp
+on u.user_id = tmp.user_id
+where DATEDIFF(day, order_date, prev) = 1 and DATEDIFF(day, pprev, prev) = 1;