SELECT d.id, d.dni, (select t.fecha from datos t where t.Evento=1 and t.Valor=0 and t.dni=d.dni and t.id<d.id order by t.id desc Limit 1) as Fecha_Salida,
 d.fecha as Fecha_Entrada, TIMESTAMPDIFF(MINUTE, (select t.fecha from datos t where t.Evento=1 and t.Valor=0 and t.dni=d.dni and t.id<d.id order by t.id desc Limit 1), d.fecha) as MINUTOS
FROM datos d
where d.Evento=1 and d.valor=1 and month(d.fecha)=month(curdate())
order by d.id desc;