Grouped Weighted Average in Access Query - sql

Question

I am trying to have a weighted average fee % of sales for each Client/Product/City combo from this data. I don't need the level of detail of sub product.
My data looks like this:
+--------+---------+-------+--------------+-------+----------------+
| Client | Product | City | Sub Product | Sales | Fee % of Sales |
+--------+---------+-------+--------------+-------+----------------+
| a | b | b | c | 1000 | 1% |
| a | b | b | d | 2000 | 2% |
| c | c | b | c | 3000 | 3% |
| d | c | b | c | 4000 | 4% |
+--------+---------+-------+--------------+-------+----------------+
I want to calculate the weighted average Fee % charged for each Client & Product combo. i.e. For Client 'a', Product 'b', City 'b': the fee% of sales would be (1,000/3,000)*1% + (2,000/3000 * 2%)
After I do this I will have another query that takes only the Client, Product,City Sales and new Weighted average field from the last query. I need another query because I will be using the results as part of a larger query.

Answer 1

This would have been easier done using window function, but since you are using ms-access... You can compute the sales subtotals per client/product/city in a subquery, and then JOIN in with the original table:
SELECT
t.client, t.product, t.city, SUM(t.sales * t.fee / t1.sales) res
FROM
mytable t
INNER JOIN (
SELECT client, product, city, SUM(sales) sales
FROM mytable
GROUP BY client, product, city
) t1
ON t1.client = t.client
AND t1.product = t.product
AND t1.city = t.city
GROUP BY t.client, t.product, t.city
This demo on DB Fiddle with your sample data returns:
| client | product | city | res |
| ------ | ------- | ---- | ------------------------------- |
| a | b | b | 0.016666666294137638 |
| c | c | b | 0.029999999329447746 |
| d | c | b | 0.03999999910593033 |

Answer 2

You can calculate the total sales & fee values as part of a subquery, then perform the division with the resulting values, e.g.:
select
q.client,
q.product,
q.city,
q.fee/q.totalsales as weightedfee
from
(
select
t.client,
t.product,
t.city,
sum(t.sales) as totalsales,
sum(t.sales*t.[fee % of sales]) as fee
from yourtable t
group by t.client, t.product, t.city
) q
Change yourtable to suit your table name.