What is the average quantity of Ikura ordered in one order?
average = AVG(Quantity); Ikura refers to ProductName = 'Ikura';
SELECT CAST(SUM(T2.Quantity) AS REAL) / COUNT(T2.OrderID) FROM Products AS T1 INNER JOIN `Order Details` AS T2 ON T1.ProductID = T2.ProductID WHERE T1.ProductName = 'Ikura'