Ver originalSELECT (SELECT SUM(valor) FROM facturaWHERE DATE_FORMAT(fecha,'%m-%Y') = DATE_FORMAT(DATE_ADD(CURRENT_DATE,INTERVAL -1 MONTH),'%m-%Y') ) - (SELECT SUM(valor) FROM facturaWHERE DATE_FORMAT(fecha,'%m-%Y') = DATE_FORMAT(CURRENT_DATE,'%m-%Y')) AS valor