- Add an Index column to be able to sort back to original order
- Group by Customer ID
- Within each subgroup:
- Add another index column to mark the first duplicate
- Transform that Index column so the 2nd row (first duplicate) is a 1 and other entries are 0's
let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSlSK1YlWSgKTyWAyEYlMwpCFkClIZCoSmQYm05ViYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}}),
//add index column to be able to sort back to original order
#"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 0, 1, Int64.Type),
//Group by the ID column (Column1 here)
//then add a column to each subgroup which has a one for the first duplicate entry (2nd entry) in each sub-table
#"Grouped Rows" = Table.Group(#"Added Index", {"Column1"}, {
{"First Duplicate", (t)=>
Table.TransformColumns(
Table.AddIndexColumn(t,"First Duplicate",0,1,Int64.Type),
{"First Duplicate", each if _ = 1 then 1 else 0})}
}),
//re-expand and sort back to original order
#"Expanded First Duplicate" = Table.ExpandTableColumn(#"Grouped Rows", "First Duplicate", {"Index", "First Duplicate"}),
#"Sorted Rows" = Table.Sort(#"Expanded First Duplicate",{{"Index", Order.Ascending}}),
#"Removed Columns" = Table.RemoveColumns(#"Sorted Rows",{"Index"})
in
#"Removed Columns"
If you want to mark the very first entry as a 1 (if there are duplicates), you can change that line in the Table.Group aggregation to mark the first entry if Table.RowCount is > 1
