update readme and add Practice Your SQL knowledge Advance level

Author: ptyadana

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

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+/**********************************************************************/
+/* SQL Queries: Practice your SQL Knowledge! */
+/**********************************************************************/
+
+/**********************************************************************/
+/* Credit to Schema : https://github.com/AndrejPHP/w3schools-database */
+/**********************************************************************/
+/* Run w3schools.sql to set up database, tables and data*/
+
+/*
+----Schema----
+Customers (CustomerID, CustomerName, ContactName, Address, City, PostalCode, Country)
+Categories (CategoryID,CategoryName, Description)
+Employees (EmployeeID, LastName, FirstName, BirthDate, Photo, Notes)
+OrderDetails(OrderDetailID, OrderID, ProductID, Quantity)
+Orders (OrderID, CustomerID, EmployeeID, OrderDate, ShipperID)
+Products(ProductID, ProductName, SupplierID, CategoryID, Unit, Price)
+Shippers (ShipperID, ShipperName, Phone)
+*/
+
+/**** Advanced Level *****/
+
+/*1. Select customer name together with each order the customer made*/
+SELECT CustomerName, OrderID
+FROM customers c
+JOIN orders o
+ON c.CustomerID = o.CustomerID;
+
+/*2. Select order id together with name of employee who handled the order*/
+SELECT o.OrderID, e.EmployeeID, e.FirstName, e.LastName
+FROM orders o
+JOIN employees e
+ON o.EmployeeID = e.EmployeeID;
+
+/*3. Select customers who did not placed any order yet*/
+SELECT c.CustomerID, c.CustomerName, o.OrderID
+FROM customers c
+LEFT JOIN orders o
+ON c.CustomerID = o.CustomerID
+WHERE o.CustomerID IS NULL;
+
+/*4. Select order id together with the name of products*/
+SELECT o.OrderID, p.ProductID, p.ProductName
+FROM orders o
+JOIN order_details od ON o.OrderID = od.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+ORDER BY o.OrderID;
+
+/*5. Select products that no one bought*/
+SELECT p.ProductID, p.ProductName, od.OrderID
+FROM products p
+LEFT JOIN order_details od ON p.ProductID = od.ProductID
+WHERE od.OrderID IS NULL;
+
+/*6. Select customer together with the products that he bought*/
+SELECT c.CustomerID, c.CustomerName, p.ProductName
+FROM customers c
+JOIN orders o ON o.CustomerID = c.CustomerID
+JOIN order_details od ON od.OrderID = o.OrderID
+JOIN products p ON p.ProductID = od.ProductID
+ORDER BY c.CustomerID, p.ProductName ASC;
+
+/*7. Select product names together with the name of corresponding category*/
+SELECT p.ProductID, p.ProductName, c.CategoryName
+FROM products p
+JOIN categories c
+ON p.CategoryID = c.CategoryID;
+
+/*8. Select orders together with the name of the shipping company*/
+SELECT o.OrderID, o.CustomerID, o.EmployeeID, o.OrderDate, shp.ShipperName
+FROM orders o
+JOIN shippers shp
+ON o.ShipperID = shp.ShipperID
+ORDER BY o.OrderID;
+
+/*9. Select customers with id greater than 50 together with each order they made*/
+SELECT c.CustomerID, c.CustomerName, o.OrderID
+FROM customers c
+JOIN orders o
+ON c.CustomerID = o.CustomerID
+WHERE c.CustomerID > 50;
+
+/*10. Select employees together with orders with order id greater than 10400*/
+SELECT o.OrderID, e.EmployeeID, e.FirstName, e.LastName
+FROM orders o
+JOIN employees e
+ON o.EmployeeID = e.EmployeeID
+WHERE o.OrderID > 10400;