SELECT FLOOR(SUM(IT.SUBTOTAL * NF.IMPOSTO)) AS IMPOSTO
FROM [NOTAS FISCAIS] AS NF
INNER JOIN (SELECT [NUMERO], [QUANTIDADE] * [PREÇO] AS SUBTOTAL FROM [ITENS NOTAS FISCAIS]) AS IT
ON NF.NUMERO=IT.NUMERO
WHERE YEAR(NF.DATA) = 2016;
