Sum IF power query

hello Anonymous 

check out this solution. Use Table.SelectRows to filter the table, then you reference the column and use the List.Sum-function to sum that column

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjLVM7DUMzJQ0lEyUIrVAQpYoAtYwgUMwQLGBmgCBoZ6hgYoAkboAiboAqZwAYgtBmbIKmIB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, flagDay = _t]),
    ChangedType = Table.TransformColumnTypes(Source,{{"Date", Date.Type, "de-DE"}, {"flagDay", Int64.Type}}),
    AddSumTil30sept20 = List.Sum(Table.SelectRows(ChangedType, each [Date]<=#date(2020,9,30))[flagDay])
in
    AddSumTil30sept20

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