How to refer to another column in a Table.TransformColumns function ?

Question

I would like to combine values from several columns of the same row in a Table.TransformColumns statement.
The solution so far involves creating a third calculated column then removing the orignal one and finally, renaming the new calculated column. I am hoping to find a simpler and more elegant solution that does not involve creating a new column.
Is it possible ? Has anyone a solution ?

Answer 1

There's no other way. You can write a function to wrap these transformations, but that function would then need to become part of your workbook as there is not yet a nice mechanism for sharing and making use of function libraries.
let
    Table.UpdateColumn = (table, column, fn) => let
        ColumnOrder = Table.ColumnNames(table),
        TmpName = Text.NewGuid(),
        InsertedCustom = Table.AddColumn(table, TmpName, fn),
        RemovedColumns = Table.RemoveColumns(InsertedCustom, {column}),
        RenamedColumns = Table.RenameColumns(RemovedColumns, {{TmpName, column}}),
        ReorderedColumns = Table.ReorderColumns(RenamedColumns, ColumnOrder)
    in
        ReorderedColumns,
    Source = Csv.Document(File.Contents("D:\test.csv"),null,null,null,1252),
    FirstRowAsHeader = Table.PromoteHeaders(Source),
    UpdatedColumn = Table.UpdateColumn(FirstRowAsHeader, "Name", each "Hello " & [Name] & "!")
in
    UpdatedColumn
For what it's worth, Table.TransformColumns is doing exactly the same steps as this under the covers.