paging pagination Power Query

How not to miss the last page when paging with Power BI and Power Query

When you use an API with a paging mechanism (like the example from this blogpost), you’ll might work with a field that contains the address for the next page. You can use this to walk through the available chunks until you reach the last element. That last element in the pagination will not contain a next-field or that field will be null.

Paging in Power Query

In Power Query you can use the function List.Generate for it. According the latest function documentation it:

Generates a list of values given four functions that generate the initial value initial, test against a condition condition, and if successful select the result and generate the next value next.

So an intuitive implementation would look like so:

paging pagination Power Query

Initial code for paging: Will miss the last element

In the initial step (row 2) the API will be called and returns this record:

paging pagination Power Query

Examining the result of the first call

So for the upcoming iterations (next in row 4), a reference to the field next will be made and this URL will be called.

In the condition (row 3) I say that this process shall be repeated until the next-field of my previous result ([Result]) is empty.

However, this will only return 14 list with 20 elements each, missing the last element with 13 items to retrieve the full 293 items.

Let’s check it out:

Last Element (13 rows) is missing

Solution

Honestly, I still find it difficult to understand, why this last element is missing. But fortunately there is an easy solution:

paging pagination Power Query

Split into 2 steps and reference previous URL instead

The trick lies in the adjusted condition (row 4): Instead of checking if there is a next-field in the previous record, I check if the previous record had a URL to call. That basically reaches 1 level further back and will deliver the full results.

Alternative

Actually, you can also use some “brute force” using a try – otherwise – statement like so:

Simple alternative

But this will not deliver any items for debugging if something in the calls goes wrong. So I prefer not to use try statements for looping or pagination.

Enjoy and stay queryious 😉

Date.Networkdays function for Power Query and Power BI

Today I’m going to share my custom NETWORKDAYS function for Power Query with you that uses the same syntax than its Excel-equivalent.

NETWORKDAYS function

This function’s first 3 parameters work just like the Excel function and there is a 4th parameter that allows adjusting the day on which the week shall start:

  1. Start as date
  2. End as date
  3. optional holidays as list of dates
  4. optional number to change the start of the week from Monday (default: 1) to any other day (2 would mean that the week starts on Tuesday instead)

The function comes with a UI that lets you first choose a table containing the holidays and then choose the column with the holiday dates. Read more

Advanced transformations on multiple columns at once in Power BI and Power Query

You can apply simple transformations to multiple columns at once in Power Query using the UI only. In this article I show how you can apply advanced transformations on multiple columns at once instead. You can also use this to use custom functions instead. And lastly for the lazyefficient fans of custom M-functions: You will get a new “TranformAllMyColumnsAtOnceHowILikeIt”-function as well 😉

Background

The Transform-tab in the query editor is sensitive to the columns you select. So if you select multiple number columns for example, some number transformations will be greyed out and are therefore not accessible:

Some symbols are greyed out, Advanced transformations on multiple columns at once in Power BI and Power Query, Power BI, Power Query, Power BI Desktop

Some symbols are greyed out

So how could I then multiply all my columns by 10 for example, as the symbol for multiplication is greyed out? Read more

Dynamically create types from text with Type.FromText in Power Query and Power BI

In this article I’ll show you how to create types from text in Power Query, enabling you to dynamically change types via functions for example. It’ll come out as a custom Type.FromText function which has been asked for in the comments of this article: https://www.thebiccountant.com/2017/01/09/dynamic-bulk-type-transformation-in-power-query-power-bi-and-m.

Problem

To transform a column to type text can be done like so:

Table.TransformColumnTypes(Source,{{"Column1", type text}})

This transforms the “Column1” from table “Source” to type text.  Now, if you want to make the type dynamic and move it to a function parameter like so:

(VariableType as type) =>

Table.TransformColumnTypes(Source,{{"Column1", VariableType}})

This returns a function dialogue as follows:

Read more

Text.RemoveBetweenDelimiters function for Power BI and Power Query

While Power Query has a native function to fetch text between 2 delimiters in Power Query, there is no such function that removes the text instead. Therefore I’ve created a custom function Text.RemoveBetweenDelimiter. It even lets you choose to remove the delimiters themselves as well via the optional 4th parameter. (“Text.RemoveBetweenDelimiters “- function)

The code for the Text.RemoveBetweenDelimiters -function

Read more