ms/access 2013 how to cumulate values in a query

There are two approaches.

1. You can use a DSUM function, so you have the field name, table, and criteria (I.e. =< the current year), or

2. You can use a self-join, and instead of using the = operator on the join, use a =<

approach 1 is simpler to do, but 2 is faster if you have a lot of data. See http://www.techonthenet.com/access/functions/domain/dsum.php for infomation on approach 1.

From the samples, I'll try this one and let you know:

DSum("UnitPrice * Quantity", "Order Details", "OrderID = 10248")

well ...
I am not getting there...

I am sending you the database; the issue is on query "_QQ" and it is the last statement. I am getting always the same number....
sireshDB-11.accdb

I'm on holiday so I can't open the database on my iPad.

However, if myYear is the year, then the code should be something like:

DSum("GrowthRate", "myTable", "myYear <= " & [myYear]) + BaseYearPop

although it still does not operate as expected, I have updated the _QQ query to what I thought could resolve the situation; bit it did not. I am uploading the novel file.
sireshDB-11.accdb

Why does it not operate as expected?

Ok. Here is the query:




code:

PopAnual: (DSum("PopPNUD_2014 * TaxaPopulacao ^anoInx";"SustentEconFin";[SustentEconFin]![anoInx]<=[anoinx] And [SustentEconFin]![RefTabanca]=[Reftabanca] And [SustentEconFin]![ano]=[ano]))

there is no sum(dsum(...))... just dsum(...)

I don't know if this is your problem but:
PopPNUD_2014 * TaxaPopulacao ^anoInx -- interpreted as PopPNUD_2014 * (TaxaPopulacao ^anoInx)
Is different from
(PopPNUD_2014 * TaxaPopulacao) ^anoInx

Whenever you write an expression that contains operators of unequal precedence, it is best to be explicit by using parentheses to specify the order of operation.

nope... that  was not the problem and I an aware of the operator precedence (actually, the formula is wrong and I am correcting it.

the problem is a bit different, let me try to put it in clearer (hopefully) words.

I have a query (_QQ) with a Population for a village. so the relevant columns are [RefTabanca] [PopPNUD_2014]  [ano] [anoinx] and [TaxaPopulacao].

[ano] is the Year (2014, 2015, ...)
[anoinx] is the ano sequence number (1 for 2014, 2 fr 2015....)
[RefTabanca] is the key code for a village
[PopPNUD_2014] is the value of the population for 2014

Now I need to compute, for each [RefTabanca] the new value of the population based on the previous year total and adding the [TaxaPopulacao] value, that varies from year to year.

The direct formula should be something like:

[ActualPopulation] :
   iif( is the first record of [RefTabanca] then
         [PopPNUD_2014];
        [ActualPopulation of previous record] * (1 + [TaxaPopulacao])
      )

so it accumulates the population over the years. I have this problem for a number of fields, this is why it is important for  me to sort it. In the end, I should have one record per year and village.

I would really appreciate any help

thanks a lot for excellent help!!!!