One example of its Power

This SQL runs in just 400 milliseconds with a database
of 10000 articles, as you can see there are several nested sql referenced.

Server:
4 Gb ram, Intel Core 2 Quad Q6600 a 2.4 GHz, HD Sata 2.

Select ID_PEDIDO_PROVEEDOR,FECHA_ENTRADA,COSTE,id_articulo,articulo,id_almacen,almacen,entradas,salidas,stock,reservado,(stock - Reservado) as DISPONIBLE
from
(
Select
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE,
ID_ARTICULO,
(Select Descripcion from MAN_ARTICULOS_DEFINIDOS
Where id_articulo = id) as Articulo,
ID_almacen,
(SELECT DENOMINACION FROM MAN_ALMACENES
WHERE ID=ID_ALMACEN) AS ALMACEN,
sum(ENTRADAS) AS ENTRADAS,
sum(SALIDAS) AS SALIDAS,
sum((ENTRADAS-SALIDAS)) AS STOCK,
(CASE WHEN Sum(RESERVADO) IS NULL THEN 0 ELSE Sum(RESERVADO) END) as Reservado

from

(
Select
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE,
ID_ARTICULO,
ARTICULO,
ID_ALMACEN,
SUM(CANTIDAD) AS ENTRADAS,

/* *********************************** CAMPO CALCULADO RESERVADO */
(Select Sum(Stock) AS RESERVADO from

(/* SQL RAIZ */
Select ID_ARTICULO,id_cab_albaran_entrada,
(Select id_almacen from Cab_albaranes_entrada
where id = id_cab_albaran_entrada) as ID_ALMACEN,
(CODIGO_ARTICULO || ' - ' || DESCRIPCION) AS articulo,
sum(CANTIDAD) AS STOCK
from LIN_ALBARANES_ENTRADA
WHERE (id_articulo = raiz.id_Articulo)
GROUP BY ID_ARTICULO,id_cab_albaran_entrada,(CODIGO_ARTICULO || ' - ' ||
DESCRIPCION)
) /* FIN - SQL RAIZ */

Group by ID_ARTICULO,ARTICULO) as RESERVADO,
/* ************************************ FIN CAMPO CALCULADO RESERVADO */
/* ************************************ CAMPO CALCULADO SALIDAS */

( Select coalesce (Sum(Stock),0 ) AS SALIDAS
from
( /* SQL RAIZ 2 */
select
ID_ARTICULO,
id_cab_albaran_SALIDA,
ID_ALMACEN_Destino,
(CODIGO_ARTICULO || ' - ' || DESCRIPCION) AS articulo,
sum(CANTIDAD) AS STOCK
from LIN_ALBARANES_SALIDA
Where (id_articulo = raiz.id_Articulo)
GROUP BY ID_ARTICULO,id_cab_albaran_salida,id_almacen_destino,(CODIGO_ARTICULO || ' - ' ||
DESCRIPCION)
)
)
/* *************************************FIN CAMPO CALCULADO SALIDAS 50 */

from

( /* SQL RAIZ */
select
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE,
ID_ARTICULO,
id_cab_albaran_entrada,
CANTIDAD,
(Select id_almacen from Cab_albaranes_entrada
where id = id_cab_albaran_entrada) as ID_ALMACEN,

(CODIGO_ARTICULO || ' - ' || DESCRIPCION) AS articulo
from LIN_ALBARANES_ENTRADA AS raiz
GROUP BY
ID_ALMACEN,
ID_ARTICULO,
(CODIGO_ARTICULO || ' - ' || DESCRIPCION),
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE,
id_cab_albaran_entrada,
cantidad

) AS RAIZ
GROUP BY
ID_ALMACEN,
ID_ARTICULO,ARTICULO,
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE) AS STOCK_TOTAL

WHERE (ID_ALMACEN = :ALMACEN) OR (:ALMACEN = 0)

GROUP BY
id_ALMACEN,ALMACEN,
ID_ARTICULO,ARTICULO,
ID_PEDIDO_PROVEEDOR,
FECHA_ENTRADA,
COSTE
ORDER BY ARTICULO,FECHA_ENTRADA,COSTE ASC

)