Adventures In Power Query Power BI Power Query

Power Query Functions ( Part 1): Introduction to Optional Parameters

You can view the final .pq query here

3 Main Methods to Declare Optional Parameters

There’s 3 main ways you can declare optional parameters in your own functions.

  1. By setting your parameter type to nullable type.

    name as text becomes
    name as nullable text

    This version requires you to always pass something, even if it’s null.

  2. By setting the type to optional like

    optional name as nullable text . You can shorten it by skipping the nullable part
    optional name as text ( Because optional parameters are implicitly nullable )

    Unlike #1, you can skip optional parameters when calling functions.

  3. By using a record parameter.

    Usually it’s a optional options as record

    This lets you call a function with any combination of keyword arguments.

  4. Merging Default Values With the User’s Record

With record parameters you can merge the user’s record with your your own default values.
It lets the user pick and choose which defaults to override — compared to using nulls as an “all-or-nothing” approach. I’ll cover this in a future post.

Creating Your Own Custom Functions

Let’s write a wrapper that calls Text.Combine . It’s a simple example to see how the parameter types differ

    Join_Nullable = (texts as list, separator as nullable text) =>
        Text.Combine( texts, separator ),

    Join_Optional = (texts as list, optional separator as text) =>
        Text.Combine( texts, separator ),

Type 1: Using Nullable Parameters

Regular nullable parameters are still mandatory. Even if it’s null.

// input [1]
Join_Nullable( chars, ", " )

// input [2]
Join_Nullable( chars, null )

// input [3]
Join_Nullable( chars )

// output [1]
a, b, c, d, e, f, g, h

// output [2]

// output [3]
Error: 1 arguments were passed
to a function which expects 2.

Type 2: Optional Parameters

If functions end with optional parameters, you can skip them entirely.

// input [1]
Join_Optional( chars, ", " )

// input [2]dfsdf
Join_Optional( chars, null )

// input [3]
Join_Optional( chars )
// output [1]
a, b, c, d, e, f, g, h

// output [2]

// output [3]

Type 3 Examples: Using Optional Records

Text.JoinString = (strings as list, optional options as record) as text => let
        Prefix    = options[Prefix]?    ?? "",
        Suffix    = options[Suffix]?    ?? "",
        Delimiter = options[Delimiter]? ?? ","
        Prefix & Text.Combine( strings, Delimiter ) & Suffix

You can mix and match any combinations of the keys Prefix, Suffix, and Delimiter .

names = {"Jen", "Hubert", "Nobody", "Somebody" },

Default       = Text.JoinString( names ) ,
AsCsv         = Text.JoinString( names, [ Delimiter = ", "] ),

AsTablePipes  = Text.JoinString( names, [
    Prefix = "| ", Delimiter = " | ", Suffix = " |" ] ),

AsBullets     = Text.JoinString( names, [
    Prefix    = " #(2022) ",
    Delimiter = " #(cr,lf) #(2022) "

Examples In The Standard Library

Type 2 Examples: Optional Parameters

When you import columns with Table.TransformColumnTypes, the UI doesn’t include the culture parameter. Unless you choose “using locale”.

// it's declared as
     table as table, typeTransformations as list,
     optional culture as text) as table

// The GUI skips the culture parameter 
= Table.TransformColumnTypes( Source,{  {"Date", type text}} )

// if you click on "locale"
= Table.TransformColumnTypes( Source,{  {"Date", type text}}, "en-GB" )

Type 3 Examples: Using Optional Records

// It's declared as
DateTime.FromText( text as nullable text, optional options as any) as nullable datetime

// without the optional parameter
= DateTime.FromText("2010-12-31T01:30:25")

// They pass 2 keyword-style arguments.
= DateTime.FromText(
     "30 Dez 2010 02:04:50.369730", 
          Format = "dd MMM yyyy HH:mm:ss.ffffff", 
     ] )

Why does DateTime.FromText use options as any and not options as record ? In this case it’s for backwards compatibility. If they were writing it from scratch today, it could have used a record. Older versions used a type text parameter.

Experiment Power BI Pwsh7+

Errors of 2023-01

Power BI

You can’t create a new table with the same name as an existing
query or item in the model.

The “New Table” button creates a new table named “Table”

This means if you create a query named “Table”, the UI cannot
create any new tables.
It’s before the rename step.

I discovered this also includes the names of disable queries.
At first I thought It was a cache—issue, but it’s not.

This is actually a good “bug”.
Which is better than if the opposite was true — letting you
create tables and expressions with ambiguous identifiers.

AI using PowerShellAI

Powershell /w the module PowerShellAI
# the original version that didn't parse 
# because ',' made number endings ambiguous
'1,000,2,000,3,000,0,000,1,000,2,000,3,000,0,000' -split '\,'
| Join-String -sep ' ' -SingleQuote
| Label 'original' -Before 1

'1000', '2000', '3000', '0', '1000', '2000', '3000'
| Join-String -sep ' ' { '{0:n0}' -f @( $_ -as 'int' ) } -SingleQuote
| Label 'should be' -Before 1 -After 1

$result ??= @{}
( $result.Steps1 ??= ai '# first 100 numbers modulous 4, multiplied by a factor of 1e6' )
| renderNice | Label 'Step1' -bef 1
label 'step3' -after 1 'This time it''s parsable, but, the numbers are not the same different.'
$result.Steps3 -split ',' -replace "'", '' | renderNice 
Experiment Power BI Power Query Uncategorized

Inspecting Function “subtypes” in Power Query

PowerQuery has metadata that you don’t normally see. For example, take the function Table.FromRecords

Create a new blank query, and set the value to a function’s name. When you reference a function without arguments or parenthesis, it displays documentation. ( It’s mostly the same as the online docs )

Where does this come from? A lot of it is generated by metadata on the function’s type itself.

Let’s start drilling down. Using the function Value.Type you can view the type’s definition

It doesn’t seem very useful at first. The data we want is from the metadata, the Ascribed types.

Metadata of the function type

The first level describes the function using specific field names that the UI looks for . The UI renders some Html from the [Documentation.LongDescription] value.

You can drill down to [Documentation.Examples] , which is a list of records.

Viewing Documenation.Examples

Function Parameters Types

There can be data defined for the arguments themselves. Parameters that are type any may have more information in their metadata.

Parameters may have metadata
Sometimes the metadata, of a parameter’s metadata — has more metadata!

Your First Function types

How do you document your own functions? Here’s a medium example. The function declared further below starts with this definition:

Text.ReplacePartialMatches_impl = (
        source as text, mapping as table
    ) as text => ...

To create the type, you start your function type almost the exact same as the definition. Then wrap it inside a type function

Text.ReplacePartialMatches.Type = type function(
        source as text,
        mapping as table
    ) as text meta [ .. ]

Next you start adding records to the final type’s metadata. If you haven’t seen the meta operator, check out Ben’s series:

The part that comes after meta operator is a regular record

    Text.ReplacePartialMatches = Value.ReplaceType( Text.ReplacePartialMatches_impl, Text.ReplacePartialMatches.Type ),
    Text.ReplacePartialMatches.Type = type function(
        source as text,
        mapping as Table.Type
    ) as text meta [
        Documentation.Name = "Text.ReplacePartialMatches",
        Documentation.LongDescription = Text.Combine({
            "Test strings for partial text matches. Replace the entire cell/value with the new replacement text.",
            "Mapping table requires two columns: <code>[Partial]</code> and <code>[New Value]</code> "

        }, "<br>")

    Text.ReplacePartialMatches_impl = ( source as text, mapping as table ) as text =>
        // todo: performance, exit early on first replacement
            mappingList = Table.ToRecords( mapping ),
            result = List.Accumulate(
                (state, cur) =>
                    if Text.Contains( state, cur[Partial], Comparer.OrdinalIgnoreCase )
                    then cur[New Value] else state
        in result


Query For the Screenshot

    Custom1 = Value.Type( Value.Type( Table.FromRecords ) ),
    fn_typeMeta = Value.Metadata( Value.Type( Table.FromRecords ) ),
    fn_typeMeta_example = ( Value.Metadata( Value.Type( Table.FromRecords ) )[Documentation.Examples]){1},
    t_fnParams = Type.FunctionParameters( Value.Type( Table.FromRecords ) ),
    fn_metaType = Value.Metadata( Type.FunctionParameters( Value.Type( Table.FromRecords ) ) ),
    type_ofFuncType = Value.Type( Type.FunctionParameters( Value.Type( Table.FromRecords ) ) [missingField] ),
    type_param_ofFuncType = Value.Metadata( Type.FunctionParameters( Value.Type( Table.FromRecords ) )[missingField] ),
    required_ofFuncType = Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ,
    type_ofRequiredType = Value.Type( Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ),
    type_ofType_ofRequiredType = Value.Metadata( Value.Type( Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ) )

Related Posts

Related Links

Related Functions

App Config Cheatsheet Getting-Started Power Apps Power BI References And Cheat Sheets

How Do I Get Started with Power Apps? With Cheat Sheets

– Moving your cursor around will change the tooltips
– It shows the data type, and the function

The Documentation Is Great

Sample Data Without a Data Source – Declaring Inline Tables

Step1: Choose Insert -> Button.

Step2: Set the button’s OnSelect property to this.

Step3: Alt left click the button, and it’ll create the table. You’re still in edit mode.

        { Name: "Fred Garcia", Company: "Northwind Traders" },
        { Name: "Cole Miller", Company: "Contoso" },
        { Name: "Glenda Johnson", Company: "Contoso" },
        { Name: "Mike Collins", Company: "Adventure Works"},
        { Name: "Colleen Jones", Company: "Adventure Works"} 

The “I know how to program, Give me the good stuff!” Section

Here’s the main links I recommend

Command Line Experiment Formatting Power BI Power Query VS Code

Experiments of 2021-10

Pwsh: Fuzzy Select Colors With Preview

PS> Get-ChildItem fg: | Where Name -match ‘red’
  • queries the color provider with partial matches
  • pipes to Out-Fzf or fzf for the preview and selection

Bitwise operators

Generated using a Pwsh script

ShouldProcess formatting

More Fzf

PSReadline: Auto-expand Aliases in the CLI

  • alt+shift+( surrounds selection, or the entire command in parenthesis
  • alt+shift+% runs Invoke-Formatter to format the code, including alias replacement

Pester5 ForEach | `code` snippet

Using Notebooks: for Github issue queries

Created a list of queries for the release of
ninmonkey/VS Code on the Web – Cheat Sheet – Custom

Power Query Web.Contents wrapper for Web API / REST calls

  • WebRequest_Simple.pq
  • enables ManualStatusHandling for better errors ( This is important for any REST APIs)
  • detects whether it’s Json or html, and returns a json record if existing
  • Always displays the response as plain-text as response_text
  • Lets you inspect request info, like headers used.

Power Query: Import from an external file

Experimenting with console formatting

Select a ton of properties, saving names as an array

Hashtables: Command line formatting

DAX: Syntax highlight bracket pairs

    "[dax-language]": {
        "editor.bracketPairColorization.enabled": true, //colorize the pairs
        "editor.guides.bracketPairs": true, // colorize vertical lines
        "editor.matchBrackets": "always",
        "editor.minimap.enabled": false,
        "editor.lineNumbers": "off",

Pwsh: Prompt that summarizes recent errors

Pwsh: Colorized Directory Listing

  • Using terminal wt, Pwsh as the shell, and module: pansies for color
  • The current directory is a gradient, the boldest part is the most important part of the path.
  • cd-ing to a directory will summarize the new directory, without “spamming” the user when there’s a lot of items
    • Folders first, sorted by most recently modified
    • Files second, sorted most recently
    • Icon shows filetype

DAX: Conditionally Toggle Button using Measure

WordPress Image scaling

link to 1:1 image
link to 1:1 image
Power BI What's New

Run DAX in Your Browser: has a DAX Web App | What’s New

The announcement:

Examples on Dax.Guide have a “try it” button to launch the editor

Cheatsheet Power BI Power Query References And Cheat Sheets

Power Query Custom Functions – Cheat Sheet

Converting Types

DateTime.FromText using format strings

let dt =  DateTime.FromText("2001-01-01T05:09:23", [Format = "yyyy-MM-ddTHH:mm:ss", Culture = "en-us"]) in dt

For format strings syntax, see: dotnet/custom-date-and-time-format-strings

Web Requests

Check out the new tutorial at

Web.Contents without Refresh Errors

The main cause of Web.Contents not refreshing can be fixed by adding the options[Query] and options[RelativeaPath] parameters. (The UI doesn’t create them for you)

This example uses See more: Skip Test Connection

// lookup city GUID - simplified
    exampleUrl = "",
    Headers = [
    BaseUrl = "",
    Options = [
        RelativePath = "/api/location/search",
        Headers = Headers,
        Query = [
            query = "london"
        ManualStatusHandling = {400, 404}
    // wrap 'Response' in 'Binary.Buffer' if you are using it multiple times
    response = Web.Contents(BaseUrl, Options),
    buffered = Binary.Buffer(response),
    response_metadata = Value.Metadata(response),
    status_code = response_metadata[Response.Status],
    final_result =
        if List.Contains({400, 404}, status_code) then response_metadata
        else buffered,
    from_json = Json.Document(final_result),
    #"weather record" = from_json{0}
    #"weather record"

Handling Specific HTTP Error Status Codes

You can filter results based on the status code, instead of getting errors.
See more: override default error handling, and the example wait-for loop

/* web request, act based on the HTTP Status Code returned
see more:
    override default error handling:
    example wait-for loop:
    WikiRequest = (pageName as text) as any =>
            BaseUrl = "",
            Options = [
                RelativePath = pageName,
                ManualStatusHandling = {400, 404}
            // wrap 'Response' in 'Binary.Buffer' if you are using it multiple times
            response = Web.Contents(BaseUrl, Options),
            buffered = Binary.Buffer(response),
            response_metadata = Value.Metadata(response),
            status_code = response_metadata[Response.Status],
            final_result = [
                buffered = buffered,
                response_metadata = response_metadata
    Queries = {"Cat", "DoesNot Exist fake page"},
    Items = List.Transform(
        each WikiRequest( _ )
    ResponseTable = Table.FromRecords(
        type table[buffered = binary, response_metadata = record], MissingField.Error

    #"Expanded HTTP Status Codes" = Table.ExpandRecordColumn(ResponseTable, "response_metadata", {"Response.Status"}, {"Response.Status"}),
    #"Changed Type" = Table.TransformColumnTypes(#"Expanded HTTP Status Codes",{{"Response.Status", Int64.Type}})
    #"Changed Type"

WebRequest: Wrapper with Better Defaults

You can get the full file with extra comments: WebRequest.pq

        Example using this url:

                [ lattlong = "36.96,-122.02" ]

        Details on preventing "Refresh Errors", using 'Query' and 'RelativePath':
            - Not using Query and Relative path cause refresh errors:

            - You can opt-in to Skip-Test:

            - Debugging and tracing the HTTP requests

        WebRequest = (
            staticPath as text,                 // domain
            relativePath as text,               // basically use everything after ".com" to "?"
            optional query as nullable record,  // url query string
            optional asRaw as nullable logical, // use true if content is not Json
            optional headers as nullable record // optional HTTP headers as a record
        ) as any =>
                query = query ?? [],
                asRaw = asRaw ?? false, // toggles calling Json.Document() or not
                headers = headers ?? [

                baseUrl = staticPath,
                options = [
                    RelativePath = relativePath,
                    Headers = headers,
                    Query = query
                    // optionally toggle handling errors for specific HTTP Status codes
                    // ManualStatusHandling = {400, 404}
                // wrap 'Response' in 'Binary.Buffer' if you are using it multiple times
                response = Web.Contents(staticPath, options),
                metadata = Value.Metadata(response),
                buffered = Binary.Buffer(response),
                result = Json.Document(buffered)
                    response = if asRaw then buffered else result,
                    status_code = metadata[Response.Status],
                    metadata = metadata

Chaining Web.Contents to Merge Many Queries

        response_locations = WebRequest(
            [ lattlong = "36.96,-122.02" ]
        location_schema = type table[
            distance = number, title = text,
            location_type = text, woeid = number, latt_long = text
        cityListing = Table.FromRecords(response_locations[response], location_schema, MissingField.Error),
        city_mergedRequest = Table.AddColumn(
            (row as record) as any =>
                    woeid = Text.From(row[woeid]),
                    response = WebRequest(
                        "api/location/" & woeid,
            type any

Html.Table – Parsing with CSS Selectors

Select a Single Element: an Image, url, text, etc…

This fetches the current heading text on the blog

    Url = "",
    Response = Web.Contents( Url ),
    note: normally do not pass dynamic urls like this, see cheatsheet on preventing refresh errors
    Non-tabular scraping like Images or any single elements, does not use a "RowSelector"

    This CSS Selector finds exactly one element, the Page's Header Text

        .section-featured-post .text-heading1 a
    HeaderText = Html.Table(
            { "Page Header", ".section-featured-post .text-heading1 a" }

Parsing Element’s Attributes

    Url = "",
    Response = Web.Contents( Url ),
    The 3rd argument in "columnNameSelectorPairs" is the transformation function.
    by default it uses:

            each _[TextContent]
    HeaderAsElement = Html.Table(
        { { "Link", ".section-featured-post .text-heading1 a", each _ } }

    ElementRecord = Table.ExpandRecordColumn(
        HeaderAsElement, "Link",
        {"TagName", "TextContent", "Attributes"}, {"TagName", "TextContent", "Attributes"}

    ExpandedAttributes = Table.ExpandRecordColumn(
        ElementRecord, "Attributes",
        {"href", "rel", "title"}, {"attr.href", "attr.rel", "attr.title"}

Select Tables using your own CSS Selectors

CSS Row Selector
Results of the RowSelector
CSS Column Selector
Results of columnNameSelectorPairs
// Docs on Enum
    Source = "",
    // note: normally do not pass dynamic urls like this, see cheatsheet on preventing refresh errors
    Response = Web.BrowserContents( Source ),

        Think of "RowSelector" as selecting a table row
        Then for every row, you select "columns" using the "columnNameSelectorPairs" selector
        The combination gives you a table cell.

        For more on CSS Selectors, see: <>

    columnNameSelectorPairs = {
        // column names don't matter here, since I'm using .PromoteHeaders
        { "Column1", "TABLE.table > * > TR > :nth-child(1)" },
        { "Column2", "TABLE.table > * > TR > :nth-child(2)" },
        { "Column3", "TABLE.table > * > TR > :nth-child(3)" }

    t1 = Html.Table(
            Response, columnNameSelectorPairs,
            [RowSelector = "TABLE.table > * > TR"]

    t2 = Table.PromoteHeaders( t1, [PromoteAllScalars = true] ),
    FinalTable = Table.TransformColumnTypes(
            { { "Name", type text }, { "Value", Int64.Type }, { "Description", type text} }

SQL Native Query

Parameterized SQL queries with Value.NativeQuery()

    Source = Sql.Database("localhost", "Adventure Works DW"),
    Test = Value.NativeQuery(
        "SELECT * FROM DimDate 
        WHERE EnglishMonthName=@MonthName",
            MonthName = "March",
            DayName = "Tuesday"


Cartesian Product

Table Cartesian Product
    #"Add Column Pair2" = Table.AddColumn(
        Table_Pairs1, "Pairs2",
        each Table_Pairs2,
    #"Expanded Pairs" = Table.ExpandTableColumn(
        #"Add Column Pair2",
        {"Color", "Property"},
        {"Color", "Property"}
    #"Expanded Pairs"


Using Multiple `Enter Data` Tables in One Query

You can make start with ‘enter data’, then duplicate that line. You end up with two steps, each are their own enter data

    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcitKzEvOLFbSUfLJrEosSgEyTJRidaKVHHNSKxJTijITgSLuqcnZ+UDaEiwTkgpS5ZtfkgGkjJRiYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Name = _t, Species = _t, Age = _t]),
    Source2 = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8krNU9JRciotKUktSsupBLINlWJ1opWCE4sSM4A858QSIGlkDBYMSU0Bclzy04GkiYFSbCwA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Name = _t, Species = _t, Age = _t]),
    Final = Table.Combine( { Source, Source2 } )

Convert Table to JSON

TableToJson = (source as table, optional encoding as nullable number) as text =>
            encoding = encoding ?? TextEncoding.Utf8,
            bin = Json.FromValue(source, encoding),
            jsonAsText = Text.FromBinary(bin, encoding)
Animals = #table(
    {"Animal", "Id"},
    {{"Cat", 1}, {"Turtle", 2}} ),
TableTo_Json( Animals )

Json output:


Converting a list of items to a CSV string

    // Converts a list of any type to text. Works well on most types
    // although to support all cases, it requires more logic
    mixedList = {4, "cat", #date(1999,5,9), 0.4},
    ListAsText = List.Transform(mixedList, each Text.From(_)),
    CsvText = Text.Combine( ListAsText, ", ")
    //output: "4, cat, 5/9/1999, 0.4"


Using Optional Parameters with Default Values

The Null_coalescing_operator ?? simplifies default values.
encoding will be set to what the user passed, unless it’s null. In that case, it is set to TextEncoding.Utf8

    Read_Json = (json as any, encoding as nullable number) as any =>
        // calls Json.Document, using UTF8 by default
            encoding = encoding ?? TextEncoding.Utf8,
            result = Json.Document(json, encoding)

Mapping Function Calls based on Type

Caller chooses which type of conversioin to use, based on type names { date, datetime, datetimezone }

    // 1] get a `type` from caller
    // 2] return a difference function based on the type
    GetTransformByType = (_type as type) as function =>
            // originally from: <>
            func_transform = 
                 if (Type.Is(_type, type date)) then Date.From
            else if (Type.Is(_type, type datetime)) then DateTime.From
            else if (Type.Is(_type, type datetimezone)) then DateTimeZone.From
            else (t) => t // else return self

    nowDtz = DateTimeZone.LocalNow(),    

    // invoke in 2 steps
    toDate = GetTransformByType(type date),
    callDate = toDate( DateTimeZone.FixedLocalNow() ),

    // create, and invoke functions
    Results = [
        asDate = (GetTransformByType(type date))( nowDtz ),
        asDateTime = (GetTransformByType(type datetime))( nowDtz ),
        asDateTimeZone = (GetTransformByType(type datetimezone))( nowDtz )
Cheatsheet Command Line Excel Power BI Power Query PowerShell

Big List of Cheat sheets and References





Other: Web



Table of Contents: Emoji Charts Table


VS Code


Windows Terminal


Other: Apps

  • .



Programming and Languages



Power Query

Dotnet / .Net



Environment Vars

Power BI Power Query

Web.Contents: Using Dynamic and Duplicate key names in a Query

Power BI Discord asked the question:
> How do you use duplicate keys, and dynamic urls with <a href="">Web.Contents</a> ?
(They were using a web API that required duplicate keys)
After I wrote this, Chris Webb found an easier solution.


  1. You can’t use a regular record because keys must be distinct. Query = [ Key1 = 1, Key1 = 10] will throw an error.
  2. You can’t put the **dynamic url** in the first argument Web.Contents or else refreshes can break

I built a RelativePath by Uri-escaping a list.

Building RelativePath by Uri-escaping a list

The final query will request the url:
This function generates the query string q=dog&q=cat

This Input"q", { "dog", "cat" }
Will Returnq=dog&q=cat
    QueryStr_UsingDuplicateKeys = (key as text, values as list) as text =>
    // values are the 'value' of 'key'-> 'value' pairs
            escapedList = List.Transform(
                    key & "=" & Uri.EscapeDataString( Text.From(_) )
            joinedArgs = Text.Combine(escapedList, "&")

Now you can use Web.Contents as normal.

    BaseUrl = "",
    queryStr = QueryStr_UsingDuplicateKeys(
        "q", {"dog", "cat"}
    Options = [
        RelativePath = "/search?" & queryStr,
        Headers = [ Accept="application/json" ]
    response_binary = Web.Contents(BaseUrl, Options)

Note: BaseUrl is for the static part of the url. Everything else should be in options[RelativePath] or options[Query] See docs: Web.Contents for details.

Easier Solution

First try Chris’s method where you use Query‘s Key-Value pairs a list
Results may vary. If it does not work, you can try this method.
I have not seen Query publicly documented.

Query = [
    q = {"dog", "cat"}

Tips from Chris Webb

Using Optional Parameters with Query

Chris has a tip to optionally use null query parameters.
If set to an empty list, {} — the request drops the parameter.
    [Query = [postId = {}] ]

Which results in the url: <a href=""></a>
This is a good place to use Power Query‘s null coalesce operator (Which isn’t in the official docs)

Query = [postId = myPostId ?? {}]

Capturing HTTP Requests without Fiddler

The Query Editor is an alternate to using Fiddler to capture web requests.
Power BI Power Query Quick Tips

Preserving Types When using “Add Custom Column” in Power Query

The default UI sets your column to type any.

You can use the optional argument of Table.AddColumn to set it to number
Or you can declare your function’s return type

Why doesn’t the original [Num] * 2 work?

Powerquery does not know what type will be returned by your function. That’s because each is by definition a function that returns type any

See More