Subtract only first value of a column

[davidz106]

I have two columns (StartTime and EndTime) where I want to create a new custom column where I subtract only first value of StartTime from each value in EndTime. Data time of both columns is Time. Suggestions appreciated.

[v-yiruan-msft · Accepted solution]

Hi @davidz106 ，

You can get it in Power Query Editor, please find the details in the attachment.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("NYzJEQAhCARz4e0DEK9JxTL/NBZhfXZP1+xNCm5UqEOUTtlUIeY8oBxs4GR7bLef4Brcb1hovX6AV3DLvwmdzsLgGWJB5AqB5oNPar8ZaWJzo7BO53w=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [StartTime = _t, EndTime = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"StartTime", type time}, {"EndTime", type time}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each [EndTime]-#"Changed Type"[StartTime]{0}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Added Custom",{{"Custom", type duration}})
in
    #"Changed Type1"

Best Regards

[amitchandak]

@davidz106 , Min and Max based on what

overall 

a new column

datediff(Min(Table[StartTime]), Max(Table[EndTime]) , second)

or based on id

datediff(MinX(filter(Table, [ID] = earlier([ID]) ),  Table[StartTime]), Max(filter(Table, [ID] = earlier([ID]) ),  Table[EndTime]) , second)

Earlier, I should have known Earlier: https://youtu.be/CVW6YwvHHi8