查看一个解释得很好的回复，该回复涉及到使用group byhere）的类似问题。
与这里描述的情况类似，因为您的查询是不明确的：每行应该使用什么“amount”。i、 e.如果您尝试：

SELECT fundid, Dateadded, ( AVG(amount) / SUM(amount) ) AS AvgRow FROM stock2 GROUP BY fundid, Dateadded ORDER BY DateAdded ASC

它将工作，因为平均（金额）是不含糊不清的每一对（基金会，dateadded）应该一起计算。
你似乎在寻找这样的东西：

SELECT st.fundid, st.Dateadded, ( amount / st2.total) ) AS AvgRow 
   FROM stock2 st 
   inner join 
      (select fundid, Dateadded, sum(amount) as total
       from stock2
       GROUP BY fundid, Dateadded) st2 
   on st.fundid = st2.fundid and st.Dateadded = st2.Dateadded
   order by st.Dateadded

这就是你想要的吗？

select t.*, t.amount / tt.total_amount
from stock2  t join
     (select fundid, dateadded, sum(amount) as total_amount
      from stock2 t
      group by fundid, dateadded
     ) tt
     using (fundid, dateadded);

还是这个？

select fundid, dateadded, sum(t.amount) / tt.total_amount
from stock2  t cross join
     (select sum(amount) as total_amount
      from stock2 t
     ) tt
 group by fundid, dateadded, tt.total_amount;