I have an OrderDetails table with a order_id field that has multiple rows of the order_id field each with a different item and quantity for the item ordered. So say, order_id = 1 and there are two items for that order. So in the OrderDetails table it has two rows for that order_id, one for each item, along with a quantity of the items. I'm not sure how I can add up the quantity of items ordered for each order_id. Everything I can think of with group by's etc. won't work. Is there anyone who can help?