> db.sales.aggregate( [ { $group : { _id : null, totalPrice: { $sum: { $multiply: [ "$price", "$quantity" ] } }, averageQuantity: { $avg: "$quantity" }, count: { $sum: 1 } } } ] )

Now look at SQL version of it and tell me which one is easier:

SELECT SUM(price * quantity), AVG(quantity), COUNT(*) FROM sales;