Filtering based on prefix match

Hi MatM,

You could use the 'fuzzy merge' option to match on Path. You may need a little trial and error to get the settings just right, but in your sample data, it worked with the defaults.

let
  Source = Table.FromRows(
    Json.Document(
      Binary.Decompress(
        Binary.FromText(
          "i45W0i/N1s/Jz0vJz9NPTs0rKUrM0U9KzMtW0lHS09MDkgpKsTpYVeUmVqYlZhaBlZCvrDy1uARDLjkxN6koMyU9FSETCwA=",
          BinaryEncoding.Base64
        ),
        Compression.Deflate
      )
    ),
    let
      _t = ((type nullable text) meta [Serialized.Text = true])
    in
      type table [Path = _t, #"Interesting data" = _t, #"Interesting data.1" = _t]
  ),
  #"Changed Type" = Table.TransformColumnTypes(
    Source,
    {{"Path", type text}, {"Interesting data", type text}, {"Interesting data.1", type text}}
  ),
  #"Merged Queries" = Table.FuzzyNestedJoin(
    #"Changed Type",
    {"Path"},
    TableB,
    {"Path"},
    "TableB",
    JoinKind.LeftOuter,
    [IgnoreCase = true, IgnoreSpace = true]
  ),
  #"Expanded TableB" = Table.ExpandTableColumn(#"Merged Queries", "TableB", {"Scope"}, {"Scope"})
in
  #"Expanded TableB"

PBIX example attached for reference.

Hope this helps.