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JillJackson's avatar
JillJackson
Qrew Member
5 months ago

DIfference between the same field in a table from the two most recent entries

Hi! My title is incorrect above and I can't seem to edit it-whoops! I am trying to set up a formula field that finds the difference between two fields in two separate entries (for the same customer) and for the two most recent entries only. For example, Entry A field X from 01/01/2022 is 98.72; Y is 50. Entry B field X from 09/06/2023 is 200. This formula field would calculate the difference (always a positive value) between B and A (X-Y) and record 150 in field Y in Entry B. Then, Entry C field X added on 10/24/2024 is 700; the difference between Entry C  X field and Entry B (most recent) Y field is recorded in field Y in Entry C...and so on always focusing on the two most recent entries by Read Date.

I have attached a screenshot of how I would like it to function; I have manually entered the data in this example. Is this possible? Or something similar?

Thank You!



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Jill Jackson
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6 Replies

  • Will you always have a set number of entries, or a relatively small max number of entries? If you have say, 5 entries max or less, you could do it with a number of summary fields. ie:

    Summary Field 1: Most Recent Value from where = Entry A
    Summary Filed 2: Most Recent Value from where = Entry B

    You would do this for the max number you would have, then look them down to the children and have a formula field that does your calculation (If Entry B, then value + Most Recent value A)

    However, if you want this to run for any number of entries, I think the only way is with formula queries. I have done something just like this, but I am careful using the values on reports, as the query can stall things out and make it pretty slow. If you can get away with a small number of summary and lookup fields, I recommend that direction, otherwise you are forced into formula queries.

    I can help with the query if that is the direction you need to go.



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    Mike Tamoush
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    • JillJackson's avatar
      JillJackson
      Qrew Member

      Hi Mike

      That'd be great. But there is no limit on entries per customer and they often exceed 5. Essentially, anything other than the most recent 2 entries are "legacy fields" for reference only. That is, every time a new entry is added the oldest of the most recent can drop off as far as the calculation or summary fields are concerned. Is there a way to restrict these summary fields' frame of reference just by setting the Read Date sort to "Group latest to earliest" and then restricting the summary to only look at those first two entries? I am new to QB so I am not sure of all its functionality/limitations, but yes-I would appreciate your help setting this up to see how it works within our app. 



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      Jill Jackson
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      • MikeTamoush's avatar
        MikeTamoush
        Qrew Commander

        So to do this, I think the only way is with formula queries. Though i will be honest, in your picture I don't understand how you got 50 for Entry A. Does it always start at 50??

        Quickbase Junkie has given some amazing resources on how to use queries:

        https://www.quickbasejunkie.com/blog/formula-query-functions?utm_source=qb&utm_medium=r&utm_id=0

        Essentially, this will take two steps.

        Step 1: Use a formula query to Rank your children by date. So earliest date is 0, then 1, then 2,3,4,5 up until the highest date.

        Step 2: Use a formula query to get the value you need from the record with the rank one below you, and use that value for your calculation.

        For step one, here is QB Junies video on ranking: https://www.quickbasejunkie.com/blog/formula-query-functions?utm_source=qb&utm_medium=r&utm_id=0

        But in summary, on your child record you will create a new formula numeric field

        [Rank]=

        var text Query = "{100.EX.'" & [Related Parent Field] & "'} AND {50.BF.'" & [Date Field] & "'}"; //where 100 is the related parent fid and 50 is the date fid

        Size(GetRecords($Query)))

        Then, Step 2 will be to get the value of the most recent Y Diff using a formula numeric field:

        [Most Recent Y Diff] = 

        var number PriorRank = [Rank]-1;

        var text Query = "{100.EX.'" & [Related Parent Field] & "'} AND {101.EX.'" & $PriorRank & "'}"; //where 100 is the related parent fid and 101 is the [Rank] fid


        ToNumber(GetFieldValues(GetRecords($Query),10)) //where 10 is the fid of the Y Difference between most recent entries

        Last step is to make your actual field you want:

        [Y Difference between most recent Entries] = [X Reading]-[Most Recent Y Diff]

        This is untested but I think it should work. Though not sure where the 50 comes from in your example, so you may have to account for that.



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        Mike Tamoush
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