Oracle查询语句的优化

请问各位大侠下面的两个SQL语句是否可以优化，现在查询速度比较慢，大约需要10秒左右
1、
SELECT GD_WPARTKEY.K_ID, GD_WPARTKEY.K_NAME, GD_WPARTKEY.C_CARTYPE,
      GD_WPARTKEY.K_REMARK, GD_WPARTKEY.U_ID, GD_WPARTKEY.F_ID,
      GD_WPARTKEY.K_WM, GD_WPARTKEY.K_XH, GF_PFACTORY.F_NAME,
      GU_UKPART.U_NAME, GD_WCOLLECTOR.C_NAME, GD_WCOLLECTOR.C_ID
from GU_UKPART, GD_WCOLLECTOR,
      GF_PFACTORY, GD_CKPART, GD_WPARTKEY
WHERE GU_UKPART.U_ID (+) = GD_WPARTKEY.U_ID AND
      GD_WPARTKEY.K_ID = GD_CKPART.K_ID AND
      GD_CKPART.C_ID = GD_WCOLLECTOR.C_ID AND
      GD_WPARTKEY.F_ID = GF_PFACTORY.F_ID AND
      (GD_WCOLLECTOR.C_ID = :CollectorID) AND
      (GD_WPARTKEY.C_CARTYPE = :CarType OR
      GD_WPARTKEY.C_CARTYPE = '0')
2、
SELECT GD_WPARTKEY.C_CARTYPE, GD_WPARTKEY.F_ID, GD_WPARTKEY.K_ID, GD_WPARTKEY.K_NAME, GD_WPARTKEY.K_REMARK,GD_WPARTKEY.U_ID, GF_PFACTORY.F_NAME, GD_CKPART.C_ID, GU_UKPART.U_NAME
from  GD_WPARTKEY  ,GD_CKPART , GF_PFACTORY,GU_UKPART
WHERE    (GD_WPARTKEY.U_ID = GU_UKPART.U_ID)AND( GD_WPARTKEY.F_ID = GF_PFACTORY.F_ID)AND(GD_WPARTKEY.K_ID = GD_CKPART.K_ID) AND( NOT EXISTS(SELECT K_ID from GD_WCARINFORKEY  WHERE  (GD_WCARINFORKEY.K_ID=GD_WPARTKEY.K_