MySQL ROLL Up question I have a table of Orders from Customers in my database for a retail store (using My SQL) and I am trying to do a ROLL UP of all orders for the month of April and for the final row to have a title of 'Grand Total' next to this total sum figure:

SELECT coalesce (OrderID, 'GrandTotal') AS OrderID, 
SUM(OrderPrice) as SumOrderPrice
FROM ORDERS 
WHERE OrderDate BETWEEN '2018-04-01' AND '2018-04-30'
GROUP BY OrderPrice WITH ROLLUP;


The problem I am having is that when I run this code, next to the total 'Sum' figure, I am getting a duplicate OrderID number, not the text 'Grand Total'. Any ideas where I'm going wrong? 
Many thanks
I'm not sure what it is you are trying to do, the GROUP BY clause that you provided is invalid. Is the following what you meant?

SELECT coalesce (OrderID, 'GrandTotal') AS OrderID, 
       SUM(OrderPrice) as SumOrderPrice
FROM ORDERS 
WHERE OrderDate BETWEEN '2018-04-01' AND '2018-04-30'
GROUP BY OrderID WITH ROLLUP;


I.e. GROUP BY OrderID instead of OrderPrice?