SQL - Sumar en Sql

SELECT

(SELECT SUM(factura.total_fac)

FROM factura

WHERE  factura.estado='A'

AND factura.id_fac

BETWEEN 59 AND 63) AS 'total',

(SELECT SUM(detalle_factura.cant_prod)

FROM detalle_factura, factura

WHERE detalle_factura.id_fac=factura.id_fac) AS 'sumacantidad',

productos.id_prod,productos.nombre_prod,detalle_factura.punitario_prod,

SUM(detalle_factura.ptotal_prod) AS 'sumaprecio',

factura.fecha_fac AS fecha,

personal.apellido_per AS 'apellido',

personal.nombre_per AS 'nombre',

personal.cedula_per AS 'cedula'

FROM factura,detalle_factura,productos, personal, asignfac

WHERE factura.id_fac

BETWEEN 59 AND 63

AND factura.id_fac=detalle_factura.id_fac

AND factura.id_fac=asignfac.id_fac

AND `asignfac`.`id_cajero`='1104592157'

AND detalle_factura.id_prod=productos.id_prod

AND factura.estado='A'

GROUP BY   detalle_factura.id_prod

SELECT p.nombre_prod as nombre, df.id_prod AS id_prod, SUM( df.cant_prod ) AS cantidad, SUM( df.ptotal_prod ) AS totdetalle,

(

select  sum(df.ptotal_prod)

FROM detalle_factura df

INNER JOIN asignfac af ON df.id_fac = af.id_fac

INNER JOIN factura f ON f.estado =  'A'

AND f.id_fac = df.id_fac

WHERE df.id_fac

BETWEEN 12

AND 18

AND af.id_cajero =  '999999999'

) as totprod,

(

SELECT SUM(f.total_fac)

FROM factura f, asignfac af

WHERE  f.estado='A'

AND af.id_fac=f.id_fac

BETWEEN 12 AND 18) AS totalfac,

(

select  sum(f.decuento)

FROM factura f

INNER JOIN asignfac af ON f.id_fac = af.id_fac

WHERE f.id_fac

BETWEEN 12

AND 18

and f.estado='A'

AND af.id_cajero =  '999999999') as descuento,

(

select  sum(f.tot_decuento)

FROM factura f

INNER JOIN asignfac af ON f.id_fac = af.id_fac

WHERE f.id_fac

BETWEEN 12

AND 18

and f.estado='A'

AND af.id_cajero =  '999999999'

)as totdescuento

FROM detalle_factura df

INNER JOIN asignfac af ON df.id_fac = af.id_fac

INNER JOIN factura f ON f.estado =  'A'

right join productos p on df.id_prod=p.id_prod

AND f.id_fac = df.id_fac

WHERE df.id_fac

BETWEEN 12

AND 18

AND af.id_cajero =  '999999999'

GROUP BY df.id_prod