Aggregate multiple rows into a single row, separating values by semicolon

Hello valcat27 

you can try this approach. First join Sales with product and expand needed column. Then join the client table. Don't expand it. Add a new column for principal client (you have to define what you mean by principal - in my example i used the maximum in clientID) and create a record for this. Add another column where you excluding the principal client from the other one joined using Table.RemoveMatchingRows and then combine the column cliendID with Text.Combine. Here the complete example... be aware that in this example I included in the first three steps your tables.

let
    Sales = let
            Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlSK1YlWMgKTxkqxsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [SalesID = _t]),
            #"Changed Type" = Table.TransformColumnTypes(Source,{{"SalesID", Int64.Type}})
        in
            #"Changed Type",
    ProductSales = let
            Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSAeJYnWglIzjLGM4yAbKMwCxTOMsMyDIGs8whrFgA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ProductID = _t, SalesID = _t]),
            #"Changed Type" = Table.TransformColumnTypes(Source,{{"ProductID", Int64.Type}, {"SalesID", Int64.Type}})
        in
            #"Changed Type",
    ClientSales = let
            Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSAeJYnWglIyDLCMwyBrKMwSwTuKwpXMwMzjKHsyzgLEu4KYYGEM2xAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ClientID = _t, SalesID = _t]),
            #"Changed Type" = Table.TransformColumnTypes(Source,{{"ClientID", Int64.Type}, {"SalesID", Int64.Type}})
        in
            #"Changed Type",

    JoinProductSalesSales = Table.NestedJoin
    (
        ProductSales,
        "SalesID",
        Sales,
        "SalesID",
        "Sales",
        JoinKind.LeftOuter
    ),
    #"Expanded Sales" = Table.ExpandTableColumn(JoinProductSalesSales, "Sales", {"SalesID"}, {"SalesID.1"}),
    JoinProductSalesSalesWithClientSales = Table.NestedJoin
    (
        #"Expanded Sales",
        "SalesID",
        ClientSales,
        "SalesID",
        "Client",
        JoinKind.LeftOuter
    ),
    #"Added Custom" = Table.AddColumn(JoinProductSalesSalesWithClientSales, "GetPrincipalClient", each Table.Max([Client],"ClientID")),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "GetOtherClients", each Text.Combine(List.Transform(Table.RemoveMatchingRows([Client],{[GetPrincipalClient]})[ClientID], each Text.From(_)), ", ")),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom1",{"Client"}),
    #"Expanded GetPrincipalClient" = Table.ExpandRecordColumn(#"Removed Columns", "GetPrincipalClient", {"ClientID"}, {"ClientID"})
in
    #"Expanded GetPrincipalClient"

The output is this

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Have fun

Jimmy