How to expand table with assigned distinctive column

Hi CornelisV,

In my solution the initial table don't have the group column as well. You can see this in the source step. I use a step on power query to add the group column.
I did some changes on my code and put all in one query, here is the M code:

let
    // Original Source
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjTWNTDUNTIwMlEwNLYyMlDSUQJhQ6VYHXRJY4gESAGmpAk+SVPcxppYGeCTNMQnice1JvhcawJxLVRnLAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Time = _t, Valve1 = _t, Valve2 = _t]),
    ChangeType = Table.TransformColumnTypes(Source, {{"Time", type datetime}, {"Valve1", Int64.Type}, {"Valve2", Int64.Type}}),
    FirstTable = Table.AddColumn(ChangeType, "Group", each 1, Int64.Type),
    SecondTable = Table.AddColumn(ChangeType, "Group", each 2, Int64.Type),
    FinalTable = Table.Combine({FirstTable, SecondTable})
in
    FinalTable

 
As you can see you only need to import one time the source and the final result is what you put oin your example.
I hope this could help you.