Get Column Name Formula

Hello Anonymous 

use this formula

Table.Min(Record.ToTable(_), "Value")[Name]

Here the full code

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("PY7BEQAhCAN74e1Hg6i1MPbfxhEY7xOZJKy4CyBNbIXoCekqt7msztlCJiM76RqNjBQ10cVmjQZI0CLEE+6kDEa7upwna7DCJJc1I3egtn7uOyoX8jJ9H+XCCu79AA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [A = _t, B = _t, C = _t, D = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"A", Int64.Type}, {"B", Int64.Type}, {"C", Int64.Type}, {"D", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each Table.Min(Record.ToTable(_), "Value")[Name])
in
    #"Added Custom"

THis is the result

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Have fun

Jimmy