Resta de dos Querys

[Jose Carlos Rey]

Otra prueba
He estado realizando cambios en la estructura de la consulta(no gran cosa, redunda practicamente en la misma) con el mismo error.
el codigo es el siguiente:

Código SQL [-]
SELECT DISTINCT a.CVE_ART, b.DESCR, a.EXIST -
                          (SELECT     z.CVE_ART, SUM(z.CANT) AS Expr1
                            FROM          PAR_FACTP02 AS z LEFT OUTER JOIN
                                                   FACTP02 AS y ON z.CVE_DOC = y.CVE_DOC
                            WHERE      (y.STATUS <> 'C') AND (z.APAR <> 0)
                            GROUP BY z.CVE_ART, z.CANT) AS Expr1, c.PRECIO
FROM         MULT02 AS a LEFT OUTER JOIN
                      INVE02 AS b ON a.CVE_ART = b.CVE_ART LEFT OUTER JOIN
                      PRECIO_X_PROD02 AS c ON a.CVE_ART = c.CVE_ART LEFT OUTER JOIN
                      PAR_FACTP02 AS d ON a.CVE_ART = d.CVE_ART LEFT OUTER JOIN
                      FACTP02 AS e ON d.CVE_DOC = e.CVE_DOC
WHERE     (e.STATUS <> 'C') AND (a.CVE_ALM = 1) AND (c.CVE_PRECIO = 1) AND (a.EXIST <> 0)
ORDER BY a.CVE_ART

si se ejecuta la consulta individual funcionan, pero al incluirlas envia el error:
"Solo se puede especificar una expresion en la lista de seleccion cuando la subconsulta no se especifica con EXIST"

consulta individual (Subconsulta): OK

Código SQL [-]
SELECT     z.CVE_ART, SUM(z.CANT) AS Expr1
FROM         PAR_FACTP02 AS z LEFT OUTER JOIN
                      FACTP02 AS y ON z.CVE_DOC = y.CVE_DOC
WHERE     (y.STATUS <> 'C') AND (z.APAR <> 0)
GROUP BY z.CVE_ART, z.CANT

consulta individual: OK

Código SQL [-]
SELECT DISTINCT a.CVE_ART, b.DESCR, a.EXIST AS EXISTENCIA, c.PRECIO
FROM         MULT02 AS a LEFT OUTER JOIN
                      INVE02 AS b ON a.CVE_ART = b.CVE_ART LEFT OUTER JOIN
                      PRECIO_X_PROD02 AS c ON a.CVE_ART = c.CVE_ART LEFT OUTER JOIN
                      PAR_FACTP02 AS d ON a.CVE_ART = d.CVE_ART LEFT OUTER JOIN
                      FACTP02 AS e ON d.CVE_DOC = e.CVE_DOC
WHERE     (e.STATUS <> 'C') AND (a.CVE_ALM = 1) AND (c.CVE_PRECIO = 1) AND (a.EXIST <> 0)
ORDER BY a.CVE_ART

como les mencione funcionan bien, pero no he logrado enlazar el resultado de una y restarle el de la otra.

Alguien que se le ocurra el origen del problema.

Gracias & saludos