add Expert level

Author: ptyadana

Diff for: SQL Queries - Practice your SQL Knowledge/SQL Queries - Practice your SQL Knowledge.mysql.sql

@@ -86,3 +86,141 @@ FROM orders o
 JOIN employees e
 ON o.EmployeeID = e.EmployeeID
 WHERE o.OrderID > 10400;
+
+/************ Expert Level ************/
+
+/*1. Select the most expensive product*/
+SELECT ProductID,ProductName,Price
+FROM products
+ORDER BY Price DESC
+LIMIT 1;
+
+/*2. Select the second most expensive product*/
+/*version 1*/
+SELECT ProductID,ProductName,Price
+FROM products
+ORDER BY Price DESC
+LIMIT 1 OFFSET 1;
+
+/*version 2 (complex)*/
+WITH
+	tbl1 AS (SELECT ProductID,ProductName,Price
+		FROM products
+		ORDER BY Price DESC
+		LIMIT 2),
+	tbl2 AS (SELECT ProductID,ProductName,Price
+		FROM products
+		ORDER BY Price DESC
+		LIMIT 1)
+        
+SELECT tbl1.ProductID,tbl1.ProductName,tbl1.Price
+FROM tbl1
+LEFT JOIN tbl2 ON tbl1.ProductID = tbl2.ProductID
+WHERE tbl2.ProductID IS NULL;
+
+
+/*3. Select name and price of each product, sort the result by price in decreasing order*/
+SELECT ProductID,ProductName,Price
+FROM products
+ORDER BY Price DESC;
+
+/*4. Select 5 most expensive products*/
+SELECT ProductID,ProductName,Price
+FROM products
+ORDER BY Price DESC
+LIMIT 5;
+
+/*5. Select 5 most expensive products without the most expensive (in final 4 products)*/
+SELECT ProductID,ProductName,Price
+FROM products
+ORDER BY Price DESC
+LIMIT 4 OFFSET 1;
+
+
+/*6. Select name of the cheapest product (only name) without using LIMIT and OFFSET*/
+WITH temp
+AS (SELECT ProductID,ProductName,MIN(Price)
+	FROM products)
+SELECT ProductName
+FROM temp;
+
+
+/*7. Select name of the cheapest product (only name) using subquery*/
+SELECT ProductName
+FROM products
+WHERE Price IN (
+	SELECT MIN(Price) FROM products
+);
+
+/*8. Select number of employees with LastName that starts with 'D'*/
+SELECT EmployeeID, LastName, FirstName
+FROM employees
+WHERE LastName LIKE 'D%';
+
+/* BONUS : same question for Customer this time */
+SELECT CustomerName, SUBSTRING_INDEX(CustomerName," ",1) AS firstName, SUBSTRING_INDEX(CustomerName," ",-1) AS lastName
+FROM customers
+WHERE  SUBSTRING_INDEX(CustomerName," ",-1) LIKE 'D%';
+
+/*9. Select customer name together with the number of orders made by the corresponding customer 
+sort the result by number of orders in decreasing order*/
+SELECT c.CustomerID, c.CustomerName, COUNT(*) AS 'TotalOder'
+FROM customers c
+JOIN Orders o
+ON c.CustomerID = o.CustomerID
+GROUP BY c.CustomerID
+ORDER BY 3 DESC, 1 ASC;
+
+/*10. Add up the price of all products*/
+SELECT SUM(Price)
+FROM products;
+
+/*11. Select orderID together with the total price of  that Order, order the result by total price of order in increasing order*/
+SELECT od.OrderID, SUM((od.Quantity * p.Price)) AS TotalValueOfOrder
+FROM order_details od
+JOIN products p ON p.ProductID = od.ProductID
+GROUP BY 1
+ORDER BY 2 ASC;
+
+/*12. Select customer who spend the most money*/
+SELECT c.CustomerID, c.CustomerName, SUM(od.Quantity * p.Price) AS TotalSpending
+FROM orders o
+JOIN customers c ON o.CustomerID = c.CustomerID
+JOIN order_details od ON o.OrderID = od.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+GROUP BY c.CustomerID
+ORDER BY 3 DESC
+LIMIT 1;
+
+/*13. Select customer who spend the most money and lives in Canada*/
+SELECT c.CustomerID, c.CustomerName, SUM(od.Quantity * p.Price) AS TotalSpending, c.Country
+FROM orders o
+JOIN customers c ON o.CustomerID = c.CustomerID
+JOIN order_details od ON o.OrderID = od.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+WHERE c.Country LIKE 'Canada'
+GROUP BY c.CustomerID
+ORDER BY 3 DESC
+LIMIT 1;
+
+/*14. Select customer who spend the second most money*/
+SELECT c.CustomerID, c.CustomerName, SUM(od.Quantity * p.Price) AS TotalSpending
+FROM orders o
+JOIN customers c ON o.CustomerID = c.CustomerID
+JOIN order_details od ON o.OrderID = od.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+GROUP BY c.CustomerID
+ORDER BY 3 DESC
+LIMIT 1 OFFSET 1;
+
+/*15. Select shipper together with the total price of proceed orders*/
+SELECT o.ShipperID, shp.ShipperName, SUM(od.Quantity * p.Price) AS TotalValueOfOrder
+FROM orders o
+JOIN order_details od ON o.OrderID = od.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+JOIN shippers shp ON shp.ShipperID = o.ShipperID
+GROUP BY 1
+ORDER BY 2;
+
+
+