I'm using SUMPRODUCT to total quaity of certain SKUS by month pulling data from the Order Items CSV Sheet. The total on the Totals sheet is only 1,167 but when I do a SUM of the QTY column in the Orders Item CSV is shows 1,411. I've also done a pivot table that came out with the same amount.
Here is where the data is stored: Order Items CSV
This is my Orders by Month and SUMPRODUCT Sheet: Orders Data Report
My formula is this:
=if(isblank($A2),0, SUMPRODUCT((MONTH('Order Items CSV'!$A$3:$A)=MONTH(DATEVALUE(B$1&"1")))('Order Items CSV'!$AG$3:$AG=$A2)('Order Items CSV'!$D$3:$D)))
I do not know why it is only totaling some of the SKUS. I've spot checked about ten SKUS through a pivot table and their Quantities are correct to what shows on the Order Data Report Sheet.
Without access to the sheet it's quite difficult to diagnose. What I can think of is something with the headers and calculations of months. A variation considering the column in which the cell is placed is:
=if(isblank($A2),0, SUMPRODUCT((MONTH('Order Items CSV'!$A$3:$A)=(COLUMN()-1))('Order Items CSV'!$AG$3:$AG=$A2)('Order Items CSV'!$D$3:$D)))
Or, for the whole table (erasing all previous formulae, and putting this in B2):
=MAKEARRAY(COUNTA(A2:A),12,LAMBDA(r,c,SUM(FILTER('Order Items CSV'!D2:D,'Order Items CSV'!AG2:AG=INDEX(A2:A,r),INDEX(MONTH('Order Items CSV'!$A$2:$A))=c))))
And, another option with QUERY, try it in a blank sheet because it will also bring the names of products:
=QUERY('Order Items CSV'!A:AG,"Select AG,SUM(D) group by AG pivot by MONTH(A)+1",1)