Name the most expensive ordered? Who, when was it ordered?
the most expensive refers to MAX(Unit Cost); who refers to Customer Names; when refers to OrderDate;
SELECT T2.OrderNumber, T1.`Customer Names`, T2.OrderDate FROM Customers AS T1 INNER JOIN `Sales Orders` AS T2 ON T2._CustomerID = T1.CustomerID INNER JOIN Products AS T3 ON T3.ProductID = T2._ProductID ORDER BY T2.`Unit Cost` DESC LIMIT 1