Código SQL:
Ver original
SELECT A.empresa,A.productor,A.ALTA,A.BAJA FROM ( SELECT empresa,productor,SELECT(MAX(fecha1)[ALTA] FROM NINC WHERE empresa=001 AND clave=5 AND fecha1<=@fFecha), SELECT(MAX(fecha1)[BAJA] FROM NINC WHERE empresa=001 AND clave=6 AND fecha1<=@fFecha) FROM ninc WHERE empresa=001 AND clave=5 AND fecha1<=@fFecha GROUP BY empresa,productor ) A WHERE A.ALTA > ISNULL(A.BAJA,1)