Restar registros de diferentes tablas !!!

[[Lepe]]

No lo he hecho antes, pero según esto sería:

Código SQL [-]
 SELECT SUM(IMP) 
FROM( select M.IMP FROM expemov M INNER JOIN EXPEDIENTES E ON E.ID = M.IDEXP         
WHERE M.IDEXP between   :EXP1 AND :EXP2            AND DH = 'D'           AND SDP = 'P' 
HAVING SUM(IMP) <> 0
union all   
select  -m.IMP FROM expemov m INNER JOIN EXPEDIENTES E ON E.ID = M.IDEXP   
WHERE M.IDEXP  between  :EXP1 AND :EXP2            AND DH = 'H'           AND SDP = 'P') AS T
AND M.IMP <> 0

MINUS

SELECT SUM(IMP) FROM EXPEPRV          WHERE IDEXP  between  :EXP1 AND :EXP2
HAVING SUM(IMP) <> 0

...me extraría que funcionase