Find the average yearly order by customer Weimei Corp for 2018, 2019 and 2020.
"Weimei Corp" is the Customer Names; in 2018, 2019 and 2020 refers to SUBSTR (OrderDate, -2) IN ('18', '19', '20') : Average order = Divide (Count (OrderNumber), 3)
SELECT COUNT(T1.OrderNumber) / 3 FROM `Sales Orders` AS T1 INNER JOIN Customers AS T2 ON T2.CustomerID = T1._CustomerID WHERE (T1.OrderDate LIKE '%/%/18' AND T2.`Customer Names` = 'Weimei Corp') OR (T1.OrderDate LIKE '%/%/19' AND T2.`Customer Names` = 'Weimei Corp') OR (T1.OrderDate LIKE '%/%/20' AND T2.`Customer Names` = 'Weimei Corp')