Posts in Category ‘DAX’

Parent-Child Hierarchies with multiple parents in Power BI with Power Query

I’ve written about a method to dynamically flatten parent-child-hierarchies also with multiple parents some while ago here. I’ve actually used this approach for Bill-of-materials cases and refined that approach in a series starting here. There, the quantities are aggregated in M already, as they are not supposed to change. But if one wants to use the hierarchical structure to report on transaction tables where several filters shall be applied, one has to adjust the data model a bit:

DimNodes

If you have parent-child-hierarchy with multiple parents, my function will a table like below, where the children with multiple parents still reside in different rows:

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Export large amount of data from Power BI desktop visuals

I’m going to show how to export data from visuals in Power BI Desktop that’s too big to be downloaded by the native functionality and therefore returns this error-message:

Export data from visuals

Check if you really need this

Although the method is fairly simple, there are simpler methods if you just need the raw data from your data model (and not the specific aggregations or measures that the visual contains): Read more

Debug DAX variables in Power BI and Power Pivot

When you’re dealing with a beast like DAX you can use any help there is, right? So here I show you how you can debug DAX variables who contain tables or show the result of multiple variables at once. So you can easily compare them with each other to spot the reason for problems fast.

Please note, that currently only comma separated DAX code is supported.

Example

Watch this measure from Gerhard Brueckl’s brilliant solution for dynamic TopN clustering with others. It contains 5 variables who return tables and one variable with a scalar:

Measure with variables who contain tables and scalars

If you want to follow along how this calculation is evolving for each value in a matrix, my VarDebugMeasure will show details of every variable like so:

Measure to debug DAX variables

Method

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DAX CALCULATE Debugger

CALCULATE is the most powerful function in DAX, as it allows you to change the filter context under which its expression is evaluated to your hearts content. But with big number of options to choose from, often comes big frustration when the results don’t match expectations. Often this is because your syntax to modify the filter context doesn’t do what you’ve intended. Unfortunately CALCULATE only displays its result and not how it achieved it, so debugging becomes a challenge. This is where my CALCULATE Debugger measure can help out:

DAX CALCULATE Debugger

This is a measure that returns a text-value, showing the number of rows of the adjusted filter context table, the MIN and MAX value of the selected column as well as up to the first 10 values. Just place this measure beneath the CALCULATE-measure in question and try to find the error 😉

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Why Power BI isn’t suitable for Financial Statements (… currently … hopefully …)

!! This is a clickbait post to get your vote for some missing features in Power BI !!

Although this might not be what the inventors of Power BI had in mind, large lots of folks are trying to create classical financial statements in it. And putting aside the afford that might go into getting the numbers right, there is still a major drawback to swallow:

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Memory efficient clustered running total in Power BI

Today I want to share a scenario where a running total calculation in the query editor saved a model that run out of memory when done with DAX:

Problem

The model couldn’t be refreshed and returned out of memory error with a calculated column in the fact table of over 20 Mio rows (from a csv-file). A running total should be calculated for each “JourneyID”, of which there were over 1 Mio in the table itself. This rose memory consumption during refresh by over 300 % – until it finally errored out:

Besetzung =
CALCULATE (
    SUM ( Fact[Entries] )
– SUM ( Fact[Exits] );
    FILTER (
        ALLEXCEPT ( Fact; Fact[JourneyID] );
Fact[StopId]
<= EARLIER ( Fact[StopId] )
    )
)

Solution

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