<code>
with verm_extras as 
(
SELECT  vrm_name, 
        ext_name
  FROM tst_vermieter, tst_fahrzeuge, tst_fhz_ext_int, tst_extras
 WHERE (    (tst_vermieter.vrm_id = tst_fahrzeuge.fhz_vrm_id)
        AND (tst_fahrzeuge.fhz_id = tst_fhz_ext_int.fei_fhz_id(+))
        AND (tst_extras.ext_id(+) = tst_fhz_ext_int.fei_ext_id)
       ) 
)
select distinct e.vrm_name, e.ext_name, nvl(extras_count, 0) c
from verm_extras e, (select vrm_name, ext_name, count(ext_name) as extras_count from verm_extras
                      group by vrm_name, ext_name) ec
where 
       ec.vrm_name = e.vrm_name and
       ec.ext_name = e.ext_name
order by e.vrm_name
</code>