What is the average number of order line items over all orders? The Sales.OrderDetails table has one row for each product for each order. Each row represents a "line item" on a sales invoice for the orderid. Start by writing a query that returns the number (COUNT) of line items (rows) for each orderid. Modify that query to CAST the line item count as decimal(8,4). Then use that query as a derived table to get the average number of line items over all orders.