Update table with rolling average from itself - sql

Question

I'm trying to update a temp table with a rolling average calculation (MS Access 2010.)
As a select query, this works to calculate a 3 month rolling average but is slow so I'd rather have the values stored and updated only when necessary:
SELECT tempQORDistGrouped.Type, tempQORDistGrouped.Supplier, tempQORDistGrouped.DepBkMo, tempQORDistGrouped.Amt, tempQORDistGrouped.Brands, tempQORDistGrouped.T2, tempQORDistGrouped.Brand, (select avg(rolavg.Amt) from tempQORDistGrouped as rolavg
where rolavg.Type = tempQORDistGrouped.Type
and rolavg.Supplier = tempQORDistGrouped.Supplier
and rolavg.Brands = tempQORDistGrouped.Brands
and rolavg.Brand = tempQORDistGrouped.Brand
and rolavg.DepBkMo between dateadd("m",-2,tempQORDistGrouped.DepBkMo) and tempQORDistGrouped.depbkmo) AS AvgAmt
FROM tempQORDistGrouped;
I've tried the update query below but I think my inner join syntax is bad as it won't recognize x1.Type as a valid field (do I need to include these as part of the inner join fields rather than in the where clause??):
UPDATE tempQORDistGrouped AS x1
INNER JOIN (SELECT itmID, avg(Amt) AS RolAvg
FROM tempQORDistGrouped
WHERE tempQORDistGrouped.Type = x1.Type
AND tempQORDistGrouped.Brand = x1.Brand
AND tempQORDistGrouped.Brands = x1.Brands
AND tempQORDistGrouped.T2 = x1.T2
AND tempQORDistGrouped.DepBkMo between dateadd("m",-2,x1.DepBkMo) and x1.DepBkMo
GROUP BY itmID
) AS x2
ON x1.itmID = x2.itmID
SET x1.3MonthRollingAmt = x2.RolAvg;
Cheers

Answer 1

Untested but should work.
I am doing a column level query to calculated the AVG and then mapping it back to the rest of the columns
Try this:
UPDATE tempQORDistGrouped AS x1
INNER JOIN (
SELECT itmID
, (
SELECT avg(Amt) amt
FROM tempQORDistGrouped x4
WHERE x4.Type = x3.Type
AND x4.Brand = x3.Brand
AND x4.Brands = x3.Brands
AND x4.T2 = x3.T2
AND x4.DepBkMo BETWEEN dateadd("m", - 2, x3.DepBkMo) AND x3.DepBkMo
) AS RolAvg
, x3.Brand
, x3.Brands
, x3.DepBkMo
, x3.T2
FROM tempQORDistGrouped x3
) AS x2
ON x1.itmID = x2.itmID
AND x1.Brand = x2.Brand
AND x1.Brands = x2.Brands
AND x1.T2 = x2.T2
AND x1.DepBkMo BETWEEN dateadd("m", - 2, x2.DepBkMo) AND x2.DepBkMo
SET x1.3MonthRollingAmt = x2.RolAvg;