Rank/Switch in M Query

Hello Anonymous 

check out this approach. Is quite complex and there might be better ways out there to do it. This is what came into my mind first. However, the code has to be adapted when you have more then 3 entrieis ond file-name/date

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcipNSspJTS/NVdJRMjbUNzTQNzIwMlCK1YlW8snPycksyC/AlMGjCUXKQN/ABLt5BvqGhkAZQ0sMTQaG+gYgKSNDQuYR6XRUq7DI4PduLAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"File Name" = _t, #"Deadline Date" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"File Name", type text}, {"Deadline Date", type date}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"File Name"}, {{"AllRows", each Table.AddIndexColumn(Table.Sort(Table.Group(_, "Deadline Date", {{"AllRows", each _}}), {{"Deadline Date", Order.Ascending}}), "Index", 1,1)}}),
    #"Removed Other Columns" = Table.SelectColumns(#"Grouped Rows",{"AllRows"}),
    #"Expanded AllRows" = Table.ExpandTableColumn(#"Removed Other Columns", "AllRows", {"Deadline Date", "AllRows", "Index"}, {"Deadline Date", "AllRows.1", "Index"}),
    #"Added Conditional Column" = Table.AddColumn(#"Expanded AllRows", "Custom", each if [Index] = 1 then "A" else if [Index] = 2 then "B" else if [Index] = 3 then "C" else null, type text),
    #"Removed Columns" = Table.RemoveColumns(#"Added Conditional Column",{"Index"}),
    #"Expanded AllRows.1" = Table.ExpandTableColumn(#"Removed Columns", "AllRows.1", {"File Name"}, {"File Name"}),
    #"Added Custom" = Table.AddColumn(#"Expanded AllRows.1", "File Name final", each [File Name]&"/"&[Custom]),
    #"Removed Columns1" = Table.RemoveColumns(#"Added Custom",{"File Name", "Custom"})
in
    #"Removed Columns1"

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy

just a variation of ...