Even though the documentation for dynamic M parameters does mention how to handle multi-select in the M code for your Power Query queries, I thought it would be useful to provide a detailed example of how to do this and explain what happens behind the scenes when you use multi-select.
If you’re familiar with the topic of query folding in Power Query, you’ll know that the View Native Query right-click option in the Applied Steps pane of the Power Query Editor can be used to show the native query that is run against the data source. You may also know that there are some data sources where query folding does take place but where View Native Query remains greyed out.
As a Power BI developer I know how Power Query makes it easy to get data from web sources, but I also know there are limits to what it can do. I can get data from tables on web pages, I can get data from web services, but when confronted with a website where you have to click a button to download a file there’s a problem.
When you’re faced with a slow Power BI report it’s very easy to assume that the problem is something to do with the dataset, how it’s modelled and how the DAX has been written, and then disappear down a rabbit hole of Marco-and-Alberto videos trying to shave milliseconds of the time taken by each DAX query the report runs.
Using a switch measure to toggle results is a mature and common technique used in Power BI and Power Pivot for Excel. For example, a switch measure can be used to toggle what appears on a chart so that the end user can easily switch the data being visualised (see image below).
In last week’s post I described the new Power Query M functions for working with Well Known Text objects, and in a post a few weeks ago I showed how you can use the Icon Map custom visual to display Well Known Text data. In this post I’ll show you how you can put all this together to do something really useful: display routes on a map in a Power BI report.
When building Power BI reports we often need to join two (or more) tables together, but what if the relationship is defined by two or more columns? Relationships in Power BI are limited to single columns, but whilst this seems like a major limitation there is actually a simple solution to create a relationship with multiple columns in Power BI.
To create a relationship with multiple columns in Power BI we simply need to create a new column by merging the required columns together. What’s more, if we use the same name in both queries Power BI will automatically create the relationship for us.