Replace values to null

Hi BatTodor,

We can use  Table.TransformColumns to meet your requirement.

    #"Table.TransformColumns"=Table.TransformColumns(previsoustep, {"ID", each if _ is number then "null" else _})

Here is the result for your reference.

The M code in power query is like this.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSgeJYnWglIyjPGMwzhvJMwTwTKM8IzDOF8kzAPDMUleYopligqLREsc/QAGFoLAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [ID = _t, Group = _t, Class = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"Group", Int64.Type}, {"Class", Int64.Type}}),
#"Table.TransformColumns"=Table.TransformColumns(#"Changed Type", {"ID", each if _ is number then "null" else _})
in
    #"Table.TransformColumns"

For more details, please check the pbix as attached.

https://www.dropbox.com/s/7sldff3q5oi0m68/replace.pbix?dl=0

Regards,

Frank