How to apply a series of steps designed for a single table to a column of tables

[JollyRoger01]

I have the following code provided by one of the very helpful users on here:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("hZBBCoAgEEXvMmsX3UdcpKagdv9tTf6GqZRgHn7wKV+tpYUMrRPImS74CSKwHQY8bogDLoHX79xHWduAV1mEcxIIKss+yxlElUVguwAd/7uxVvH+hFxf3Rp6Z+Sm91neUbwg9693Bw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [#"(blank)" = _t, #"20201218" = _t, #"20201221" = _t, #"20201222" = _t, #"20201223" = _t, #"20210104" = _t, #"20210105" = _t, #"20210106" = _t]),
    checkBlank = Table.CombineColumns(Source, Table.ColumnNames(Source), (x)=> if List.MatchesAll(x,each _ = "") then 1 else 0,"check"),
    #"Added Index" = Table.AddIndexColumn(checkBlank, "Index", 0, 1),
    #"Added Custom" = Table.AddColumn(#"Added Index", "Group", each if [Index]=0 then 0 
else if [check] = 0 then List.Sum(List.FirstN( checkBlank[check], [Index])) 
else -1),
    SouceIndex = Table.AddIndexColumn(Source, "Index", 0,1),
    #"Merged Queries" = Table.NestedJoin(SouceIndex, {"Index"}, #"Added Custom", {"Index"}, "Group", JoinKind.LeftOuter),
    #"Expanded Group" = Table.ExpandTableColumn(#"Merged Queries", "Group", {"check", "Group"}, {"check", "Group"}),
    #"Filtered Rows" = Table.SelectRows(#"Expanded Group", each ([check] = 0)),
    #"Removed Columns" = Table.RemoveColumns(#"Filtered Rows",{"Index", "check"}),
    #"Grouped Rows" = Table.Group(#"Removed Columns", {"Group"}, {{"allrows", each _, type table }}),
    #"Promote Headers" = Table.TransformColumns(#"Grouped Rows", {{"allrows", each Table.PromoteHeaders(_, [PromoteAllScalars = true])}})
in
    #"Promote Headers"

That results in a column of tables and I have named the query 'Tabulated'. I also have the below code that I was planning to apply individually to all of the tables once I expanded them out, but I figured I should be able to do it to all tables before expanding them. It basically removes all the columns that are 0 or blank.

let
    Source = Tabulated,
    #"1" = Source{[Group=1]}[allrows],
    Custom1 = Table.ColumnNames(#"1"),
    #"Converted to Table" = Table.FromList(Custom1, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Added Custom" = Table.AddColumn(#"Converted to Table", "Custom", each [a=Table.Column(#"1", [Column1]),
b=List.MatchesAll( a, each _ ="0") or List.MatchesAll( a, each _ ="")][b]),
    #"Filtered Rows" = Table.SelectRows(#"Added Custom", each ([Custom] = false)),
    Custom2 = Table.SelectColumns(#"1",  #"Filtered Rows"[Column1])
in
    Custom2

I would like to know how I encapsulate all this and apply it within the previous query so all the columns with zero or blank values are removed from all the tables before I expand them out.

[watkinnc]

Are you concerned that by removing columns from what might be just some of the tables,that when you expand them, the missing column values will be null anyway, assuming you are accounting for that with a MissingField parameter? Or would you prefer to removed ROWS with blanks and zeros from the nested tables?

[Vera_33 · Accepted solution]

Hi @JollyRoger01 

you can convert the second one to a function, and modified your drill down table a little bit, added 0 as you do have digit instead of any type

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("hZBBCoAgEEXvMmsX3UdcpKagdv9tTf6GqZRgHn7wKV+tpYUMrRPImS74CSKwHQY8bogDLoHX79xHWduAV1mEcxIIKss+yxlElUVguwAd/7uxVvH+hFxf3Rp6Z+Sm91neUbwg9693Bw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [#"(blank)" = _t, #"20201218" = _t, #"20201221" = _t, #"20201222" = _t, #"20201223" = _t, #"20210104" = _t, #"20210105" = _t, #"20210106" = _t]),
    checkBlank = Table.CombineColumns(Source, Table.ColumnNames(Source), (x)=> if List.MatchesAll(x,each _ = "") then 1 else 0,"check"),
    #"Added Index" = Table.AddIndexColumn(checkBlank, "Index", 0, 1),
    #"Added Custom" = Table.AddColumn(#"Added Index", "Group", each if [Index]=0 then 0 
else if [check] = 0 then List.Sum(List.FirstN( checkBlank[check], [Index])) 
else -1),
    SouceIndex = Table.AddIndexColumn(Source, "Index", 0,1),
    #"Merged Queries" = Table.NestedJoin(SouceIndex, {"Index"}, #"Added Custom", {"Index"}, "Group", JoinKind.LeftOuter),
    #"Expanded Group" = Table.ExpandTableColumn(#"Merged Queries", "Group", {"check", "Group"}, {"check", "Group"}),
    #"Filtered Rows" = Table.SelectRows(#"Expanded Group", each ([check] = 0)),
    #"Removed Columns" = Table.RemoveColumns(#"Filtered Rows",{"Index", "check"}),
    #"Grouped Rows" = Table.Group(#"Removed Columns", {"Group"}, {{"allrows", each _, type table }}),
    #"Promote Headers" = Table.TransformColumns(#"Grouped Rows", {{"allrows", each Table.PromoteHeaders(_, [PromoteAllScalars = true])}}),
    
    fxRemoveColumns = (x as table) =>
    let
    Source = x,
    Custom1 = Table.ColumnNames(Source),
    #"Converted to Table" = Table.FromList(Custom1, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Added Custom" = Table.AddColumn(#"Converted to Table", "Custom", each [a=Table.Column(Source, [Column1]),
b=List.MatchesAll( a, each _ ="0") or List.MatchesAll( a, each _ ="") or List.MatchesAll( a, each _ =0)][b]),
    #"Filtered Rows" = Table.SelectRows(#"Added Custom", each ([Custom] = false)),
    Custom2 = Table.SelectColumns(Source,  #"Filtered Rows"[Column1])
in
    Custom2,
    
    AddTableColumn = Table.AddColumn(#"Promote Headers","new", each fxRemoveColumns([allrows]))
in
    AddTableColumn