(
	CAST( SUM( r.price ) AS FLOAT ) /
	(
		SELECT
			dbo.ISZERO( SUM( r2.price ), 1 )
		FROM
			reward r2
		INNER JOIN
			[order] o2
		ON
			r2.order_id = o2.id
		WHERE
			o2.user_id = u.id
	) *
	100
) AS percentage_used