Use Northwind
--Practica 1
SELECT ProductName, UnitPrice 
FROM Products
WHERE UnitPrice > (
 SELECT AVG (UnitPrice)
 FROM Products );
 

 --Practica 2

Select ContactName
From Customers
Where CustomerID in (Select distinct CustomerID from Customers)

 --Practica 3

SELECT pp.ProductName, AVG(pp.Price) AS AvgPrice
FROM (
    SELECT p.ProductName, c.CategoryID, p.UnitPrice AS Price
    FROM Products p
    JOIN Categories c ON p.CategoryID = c.CategoryID
) AS pp
GROUP BY pp.ProductName;
