我有一個TABLE，其欄位為：代號、名稱、日期、金額
每日我要去計算該代號的最後10筆交易的平均金額，SQL如下：

select no,name,b.nn
from (select no,name
from detail
group by 1,2
)a
left join
(select no,name,avg(price) as nn
from detail a,
(select min(a.date) as aa,max(a.date) as bb
from (select date
from detail
where date<=from_days(to_days(now())-10)
group by 1 desc
limit 0,10
)a
)b
where date>=b.aa
and date<=b.bb
group by 1,2
)b
on a.no=b.no
group by 1,2
;

但有些代號不是每日都會有交易，上述的SQL所計算出的平均價就不是10筆的平均，
而是看它有幾筆，就是幾筆的均價
請問大家，我該如何找出每項代號的最後10筆交易，並計算平均價

謝謝大家