How to delete the last column of data without referencing column names?

[JollyRoger01]

I have data that includes a total column at the end that summed across the rows. I want to delete this column, but I can't click on it and delete it as the column name may change when the data source is updated, causing errors. So I am looking for a function of some type that deletes the last column and won't cause any errors if all the column names in the source are changed.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("VVFLEoUwCLuLaxcC/dizON7/Go+kTZ23MKMCCQnPc5RxnIdFgjdAPqUkBMA63vBcCTf+3KvJSzve85kD/LnBWDdAFbnxk1R1f9ZOCqqwFZqFjEPqFDQWMFOxCBYteIlkJAOaunhZIh/XdsBY+3O+yp82QDW+IEz10KhBMmy7qYvF0w0I6J1hoVyafLjLhw+1cJ+4t1CKMEgOMYXQEXZoE7pmbPwVIv0zhqqsoq9AuHO4DA3pk2FGTWvXvGYoHp606aJzIypfsv+dg5tH9rzvDw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"20201218" = _t, #"20201221" = _t, #"20201222" = _t, #"20201223" = _t, #"20210104" = _t, #"20210105" = _t, #"20210106" = _t, #"20210107" = _t, #"20210108" = _t, #"20210110" = _t, #"20210111" = _t, #"20210112" = _t, #"20210113" = _t])
in 
    Source

[watkinnc]

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("VVFLEoUwCLuLaxcC/dizON7/Go+kTZ23MKMCCQnPc5RxnIdFgjdAPqUkBMA63vBcCTf+3KvJSzve85kD/LnBWDdAFbnxk1R1f9ZOCqqwFZqFjEPqFDQWMFOxCBYteIlkJAOaunhZIh/XdsBY+3O+yp82QDW+IEz10KhBMmy7qYvF0w0I6J1hoVyafLjLhw+1cJ+4t1CKMEgOMYXQEXZoE7pmbPwVIv0zhqqsoq9AuHO4DA3pk2FGTWvXvGYoHp606aJzIypfsv+dg5tH9rzvDw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"20201218" = _t, #"20201221" = _t, #"20201222" = _t, #"20201223" = _t, #"20210104" = _t, #"20210105" = _t, #"20210106" = _t, #"20210107" = _t, #"20210108" = _t, #"20210110" = _t, #"20210111" = _t, #"20210112" = _t, #"20210113" = _t]),
#"New" =  let max = Table.ColumnCount(Source) in Table.RemoveColumns(Source, {Table.ColumnNames(Source){max - 1}})
in
#"New"

--Nate

[JollyRoger01]

Thank you for this. I'm still learning M and am a little confused with the 'let' here. Are you able to explain a little about how it works and why it is used here?

[JollyRoger01]

I may have solved it, but if anyone has a better way please let me know. I would like to know how to hide the variable name 'max' from the Applied Steps list.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("VVFLEoUwCLuLaxcC/dizON7/Go+kTZ23MKMCCQnPc5RxnIdFgjdAPqUkBMA63vBcCTf+3KvJSzve85kD/LnBWDdAFbnxk1R1f9ZOCqqwFZqFjEPqFDQWMFOxCBYteIlkJAOaunhZIh/XdsBY+3O+yp82QDW+IEz10KhBMmy7qYvF0w0I6J1hoVyafLjLhw+1cJ+4t1CKMEgOMYXQEXZoE7pmbPwVIv0zhqqsoq9AuHO4DA3pk2FGTWvXvGYoHp606aJzIypfsv+dg5tH9rzvDw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"20201218" = _t, #"20201221" = _t, #"20201222" = _t, #"20201223" = _t, #"20210104" = _t, #"20210105" = _t, #"20210106" = _t, #"20210107" = _t, #"20210108" = _t, #"20210110" = _t, #"20210111" = _t, #"20210112" = _t, #"20210113" = _t]),
    max = Table.ColumnCount(Source),
    #"New" = Table.RemoveColumns(Source, {Table.ColumnNames(Source){max - 1}})
in
    #"New"