只需将第二个select语句用子查询 Package 起来：

select avg("JUMLAH") 
from(select d.nama,count(th.fk_distributor) as "JUMLAH"
     from mh_distributor d join 
          th_beli th on th.fk_distributor = d.kode
     group by d.nama
    ) t;

所以，你的完整陈述应该是：

select d.kode, rpad(d.nama,75,' ') as "NAMA", 
      lpad(count(th.fk_distributor),10,' ') as "JUMLAH"
from mh_distributor d join 
     th_beli th 
     on th.fk_distributor = d.kode
having count(td.fk_produk) > (select avg("JUMLAH") 
                              from(select d.nama,count(th.fk_distributor) as "JUMLAH"
                                   from mh_distributor d join 
                                        th_beli th on th.fk_distributor = d.kode
                                   group by d.nama
                                 ) t
                             )
group by d.nama, td.fk_produk, d.kode
order by d.kode asc;

使用窗口函数！

select nk.*
from (select d.kode, d.nama, count(*) as jumlah,
             avg(count(*)) over (partition by d.nama) as avg_jumlah
      from mh_distributor d join
           th_beli th
           on th.fk_distributor = d.kode
      group by d.nama, td.fk_produk, d.kode
     ) nk
where jumlah > avg_jumlah;

我省略了到字符串的转换，因为我认为这只会使逻辑更难遵循--当然，针对您的特定用例，将其添加回外部查询中。
这应该比复杂的having子句有更好的性能。