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Anonymous's avatar
Anonymous
Not applicable
3 years ago

Table.FirstN function doesn't seem to work properly for my case...

Hello, Here is my code for which I don't understand the output : let Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ndQ9bsMwDAXg3acQvDYWSOrP1lWCDBocJEVbF4085PaVOrSMHa...
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Anonymous's avatar
Anonymous
Not applicable
3 years ago

Hi,

Thanks for the workaround, it is indeed working with SelectRows. The logic has to be like this though in order to be like what was expected with FirstN/LastN :

#"Added JobStarted" = Table.AddColumn(Custom1, "JobStarted", each Table.Last(Table.SelectRows([Custom], each [Isuserpartofteama] = true))[Creationdate], type datetimezone),
#"Added JobEnded" = Table.AddColumn(#"Added JobStarted", "JobEnded", each Table.First(Table.SelectRows([Custom], each [Isuserpartofteama] = false))[Creationdate], type datetimezone),

But it actually doesn't answer why it is not working with FirstN/LastN ? Indeed, why for instance "each Table.FirstN([Custom], each [Isuserpartofteama] = false)" returns empty tables for the 1st and 4th line ? I keep reading the documentation and it should work, what is wrong with it please ?

Regards,

  • lbendlin's avatar
    lbendlin
    Super User
    3 years ago

    Welcome to the wonderful world of contexts.  Yes, they exist in Power Query too.  You are nesting one "each"  inside another "each"  and Power Query gets confused as to which context to use.  

     

    Mitigate by using inline functions or variables ("let ... in ..." ) much like you would do in DAX.

    • Anonymous's avatar
      Anonymous
      Not applicable
      3 years ago

      But I have as many "each" involved/nested in my original code mixing Last/FirstN that I have in the Last/SelectRows version, so why is the context "clearer" in the second case ? Do parenthesis would help regarding this context issue ? Is this a known issue that Microsoft is going to address soon ? This seems crazy.. I mean my code is not yet very complicated and I can't already be sure that it is behaving as expected ? How can I check/debug what context is being use ?