Calculate days between dates on 2 different rows

Hi TeisL ,

In summary, the steps are: Split columns-->Groupby -->Add Custom -->Expand and remove,

Below is the whole M syntax:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("fdBNCoBACAXgu8y6ePrsZ9xG+w4Q3f8aWVBMNAUuhA986romlaFd5tQkdRf0IKNPW/OQ3kEUkNvpgCiKEEqY1sj+aIDJLWcQRUdkUMukSyyWqwH1GyK9JtJBy3P8ujPHtvAXxCw7HjCesu0=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [WKN = _t, #"Start OD Date" = _t, #"Stop BD Date" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"WKN", type text}, {"Start OD Date", type date}, {"Stop BD Date", type date}}),
    #"Duplicated Column" = Table.DuplicateColumn(#"Changed Type", "WKN", "WKN - Copy"),
    #"Split Column by Delimiter" = Table.SplitColumn(#"Duplicated Column", "WKN - Copy", Splitter.SplitTextByDelimiter("-", QuoteStyle.Csv), {"WKN - Copy.1", "WKN - Copy.2"}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Split Column by Delimiter",{{"WKN - Copy.1", Int64.Type}, {"WKN - Copy.2", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type1", {"WKN - Copy.1"}, {{"Count", each _, type table [WKN=nullable text, Start OD Date=nullable date, Stop BD Date=nullable date, #"WKN - Copy.1"=nullable number, #"WKN - Copy.2"=nullable text]}}),
    #"Added Custom" = Table.AddColumn(#"Grouped Rows", "Custom", each [
max=Record.Field( Table.Max([Count] ,"Stop BD Date"),"Stop BD Date"),
min=Record.Field(Table.Min(Table.SelectRows([Count],each [Start OD Date] <>null ),"Start OD Date"),"Start OD Date"),
diff=Duration.Days(max-min) 
][diff]),
    #"Expanded Count" = Table.ExpandTableColumn(#"Added Custom", "Count", {"WKN", "Start OD Date", "Stop BD Date"}, {"WKN", "Start OD Date", "Stop BD Date"}),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded Count",{"WKN - Copy.1"})
in
    #"Removed Columns"

Best Regards,
Eyelyn Qin
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