--Heiko Hommes

select count(*), durch_bon_grp
from 
(
select 
  CASE
    WHEN durch_bon between 0 and 20 then 'bis 20'
    WHEN durch_bon between 21 and 30 then 'bis 30'
    WHEN durch_bon between 31 and 50 then 'bis 50'
    WHEN durch_bon between 51 and 70 then 'bis 70'
    WHEN durch_bon between 71 and 100 then 'bis 100'
    WHEN durch_bon between 101 and 150 then 'bis 150'
    WHEN durch_bon between 151 and 200 then 'bis 200'
    ELSE
         'über 200'
    end durch_bon_grp
    
   FROM 
   (
    select kdnr, round(avg(betrag)) durch_bon from transaktion
       where to_char(datum_bon,'yyyymm') in ('200611','200612')
          and bereich=3
          and kdnr > 9999
    group by kdnr
   )
)
group by durch_bon_grp