I think what you're trying to do is join with only the first instance of each value in your Customer
column. There doesn't appear to be any feature or GUI element that allows you to do that (I had a look at the reference documentation for Power Query M, maybe I missed something).
To replicate your data, I'm starting off with some tables (left table is namedCustomers
, right table is namedOrders
):
I then use the M
code below (the first few lines are just to get my tables from the sheet):
let
customers = Excel.CurrentWorkbook(){[Name = "Customers"]}[Content],
orders = Excel.CurrentWorkbook(){[Name = "Orders"]}[Content],
merged = Table.NestedJoin(orders, {"CUSTOMER"}, customers, {"CUSTOMER"}, "merged", JoinKind.LeftOuter),
indexColumn = Table.AddIndexColumn(merged, "Temporary", 0, 1),
indexes =
let
uniqueCustomers = Table.Distinct(Table.SelectColumns(indexColumn, {"CUSTOMER"})), // Want to keep as table
listOfRecords = Table.ToRecords(uniqueCustomers),
firstOccurenceIndexes = List.Accumulate(listOfRecords, {}, (listState, currentItem) =>
List.Combine({listState, {Table.PositionOf(indexColumn, currentItem, Occurrence.First, "CUSTOMER")}})
)
in
firstOccurenceIndexes,
expandSelectively =
let
toBoolean = Table.TransformColumns(indexColumn, {{"Temporary", each List.Contains(indexes, _), type logical}}),
tableOrNull = Table.AddColumn(toBoolean, "toExpand", each if [Temporary] then [merged] else null),
dropRedundantColumns = Table.RemoveColumns(tableOrNull, {"merged", "Temporary"}),
expand = Table.ExpandTableColumn(dropRedundantColumns, "toExpand", {"FUNDING"})
in
expand
in
expandSelectively
If your table names and column names match mine (including case sensitivity), then you might just be able to copy-paste all of the M
code above into the Advanced Editor and have it work for you. Otherwise, you may need to tweak as necessary.
This is what I get when I load the query to the worksheet.
There might be better (more efficient) ways of doing this, but this is what I have for now.