Power Query for Azure Tables and
Updating Column Names

I recently did some PowerBI work using Azure Table Storage. In the query editor, it seemed that each table I pulled in from Azure Tables had a very similar process.:

  1. Get the list of tables available for the storage account.
  2. Select a table
  3. Select the Content of the table (excluding the RowKey, PartitionKey, and timestamp columns)
  4. Expand the columns in the Content
  5. Rename the columns

Azure table column names don’t allow spaces, but they are case-sensitive, so I found that if I was careful to use PascalCasing in my Azure Table columns (which I am careful to do in any storage container), I could adapt the steps above to make a function that would do all those things for me, just by providing the name of the account and the name of the table.

let GetAzTable = (account as text, table as text) =>
  Source = AzureStorage.Tables(account),
  Table1 = Source{[Name=table]}[Data],
  ContentOnly = Table.SelectColumns(Table1,{"Content"}),
  ColumnName = Table.ColumnNames(ContentOnly){0},
  Content = Table.Column(Table.FirstN(ContentOnly,100),ColumnName),
  ColumnsToExpand = List.Distinct(List.Combine(List.Transform(Content,
    each if _ is record then Record.FieldNames(_) else {}))),
  NewColumnNames = List.Transform(ColumnsToExpand, each NewColumnName(_)),
  ExpandedContent = Table.ExpandRecordColumn(ContentOnly, ColumnName, ColumnsToExpand,NewColumnNames)
in GetAzTable

In this code, I reference another function that generates the new “nice” column name based on the column name in the Azure table. This function doesn’t do the name formatting, but it determines if a column should get a nice name or not. I use a naming convention for columns that are meant to be used internally – either as a join key or for a sort column, or for a measure calculation. This function returns the column name “as is” if it follows the naming convention for internal columns, or calls the function GetPascalName to make it a “nice” name.

let NewColumnName = (colName as text) as text =>
  Source = if Text.EndsWith(colName, "Key") or Text.EndsWith(colName,"Num") or Text.EndsWith(colName, "Sort") or Text.EndsWith(colName,"SortOrder") or colName = Text.Upper(colName) then colName else GetPascalName(colName)
in NewColumnName

Here is the cool code:

let PascalName = (pascalName as text) as text =>
  Source = Text.ToList(pascalName),
  Caps = { "A" .. "Z" },
  NewSource = List.Combine(List.Transform(Source, (x) => if List.PositionOf(Caps, x) >= 0 then {" ",x} else {x})),
  result = Text.Trim(Text.Combine(NewSource, ""))
in PascalName

This code takes a text value and turns it into a list (of individual characters). Then it recombines the list of characters, adding a space before each capital letter. Finally, it trims the leading space.

This isn’t perfect by all means – it could be improved by only putting a space in front of the first capital in a series of capitals. A column named “FTPUrl” will come back as “F T P Url”. (Note that I’ve already caught the case of a column with ALLCAPS in the NewColumnName function.) Just looking at this edge case, I think the algorithm would need to put a space before the first and the last capital in a series of capitals (” FTP Url”, trimmed to “FTP Url”).

You can view the original post of the author here

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