Update a column in a collection based on the value in that column

[edhalsim]

Hi

I have a collection as follows:

Name	Quantity
Ed	8
Tom	3
Alan	1

I need to update these records based on new records in a specified order:

Name	Quantity
Ed	-3
John	13

So my final collection will be:

Name	Quantity
Ed	5
Tom	3
Alan	1
John	13

I'm looping through each new row in order using a ForAll.  I don't know how to update the Quantity based on the existing Quantity, something like:

Patch(

    Rows,

    LookUp(

        Rows,

        Rows[@Name]=NewRow[@Name]

    ),

    {

        Quantity=Quantity+NewRow[@Quantity]

    }

)

Any help would be appreciated.  Thanks.

[CNT]

@edhalsim 

Please try the following (replace collection names as applicable),

ClearCollect(colCombined, DropColumns(AddColumns(GroupBy(Collect(col1, col2), "Name", "GroupedData"), "Quantity", Sum(GroupedData, Quantity)), "GroupedData"));

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[edhalsim]

Wow.  This is beyond my current level of understanding.  Would you please explain what you're doing?

[CNT · Accepted solution]

@edhalsim Absolutely simple!

Just have to see it from inside out.

1. Combining the two collections, Collect(col1, col2)
2. Grouping them on the Name as its the Key. Call this Group as "Grouped Data". The result of this will have the "Name" Column and a "Grouped Data" Column. This "Grouped Data" Column will have the Quantity for each person (E.g. it will have 2 records for Ed, 8 & -3)
3. Add a Column called Quantity, and set its value as the Sum of the Quantity in the "Grouped Data" (E.g. for Ed, it will be Sum(8, -3) and the result is 5).
4. Drop the "Grouped Data" Column as we don't need it any more.
5. Store the results in another collection.
6. Time for an Ice Cream!

Please remember to give a 👍 and accept my solution as it will help others in the future.