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Anonymous's avatar
Anonymous
Not applicable
4 years ago

Lead function, with partition by and order by in Power Query

Hello guys, i need help to replicate the same function i have in sql to power query. I need to bring the result of the previous row of the column "ORGANIZATION_UNIT_ID" partitioned by a cluster which...
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Vijay_A_Verma's avatar
Vijay_A_Verma
Most Valuable Professional
4 years ago

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("dc9BDoAgDETRu7Am6UwR4l2I97+GSAxooSsWLxP6aw2JQohCGWJQAO1huGITCLmXtlFP0Dc6RbvoKdCtPJu0FwgOI/OfvJe2KUbSuHqU0i2lW0p79SilW0pzwSx9Ja+lf/mWLpuyynUD", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [LOAD_DATE = _t, GLOBAL_EMPLOYEE_ID = _t, ORGANIZATION_UNIT_ID = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"LOAD_DATE", type text}, {"GLOBAL_EMPLOYEE_ID", Int64.Type}, {"ORGANIZATION_UNIT_ID", Int64.Type}}),
    ListOfIDs = List.Buffer(#"Changed Type"[GLOBAL_EMPLOYEE_ID]),
    ListOfValues = List.Buffer(#"Changed Type"[ORGANIZATION_UNIT_ID]),
    GenList = List.Generate(()=>[x=null,i=0], each [i]<List.Count(ListOfValues), each [i=[i]+1, x=(if ListOfIDs{i}=ListOfIDs{[i]} then ListOfValues{[i]} else null)], each [x]),
    Result = Table.FromColumns(Table.ToColumns(#"Changed Type")&{GenList},Table.ColumnNames(#"Changed Type")&{"Last_Organization_Unit_ID"})
in
    Result
artpil's avatar
artpil
Resolver II
4 years ago

Hi Vijay,

This is great code. Can you explain what's going on in this code?

List.Generate(()=>[x=null,i=0], each [i]<List.Count(ListOfValues), each [i=[i]+1, x=(if ListOfIDs{i}=ListOfIDs{[i]} then ListOfValues{[i]} else null)], each [x])

What I undestood is:

()=>[x=null,i=0] - this creates record object with values x=null and i=0

each [i]<List.Count(ListOfValues) - this checks if iteration is smaller then number of items in list

each [i=[i]+1, x=(if ListOfIDs{i}=ListOfIDs{[i]} - this creates record with column i equal i + 1 and column x - here I don't understand what is happening. ListOfIDs{i} means get element i from list ListOfIDs but what does it does ListOfIDs{[i]} ?

last part returns x calculated earlier.

Thanks in advance for your explanantion.

Artur

  • Vijay_A_Verma's avatar
    Vijay_A_Verma
    Most Valuable Professional
    4 years ago

    i = [i]+1, hence in ListOfIDs{i}=ListOfIDs{[i]}, I can also use ListOfIDs{i}=ListOfIDs{i-1} => I am checking wether current value of list is = previous value of list or not. If it is equal, it means same group continues. If it is unequal, then a new group has started. If a new group is started, then result should be null. If within same group, then value is ListOfValues{[i]} where [i] means i-1. So I could have written it ListOfValues{i-1} as well.