Book Image

Learn Power Query

By : Linda Foulkes, Warren Sparrow
Book Image

Learn Power Query

By: Linda Foulkes, Warren Sparrow

Overview of this book

<p>Power Query is a data connection technology that allows you to connect, combine, and refine data from multiple sources to meet your business analysis requirements. With this Power Query book, you’ll be empowered to work with a variety of data sources to create interactive reports and dashboards using Excel and Power BI. </p><p>You’ll start by learning how to access Power Query across different versions of Excel and install the Power BI engine. After you've explored Power Pivot, you’ll see why Excel users find it challenging to clean data in Power Pivot and learn how Power Query can help to tackle the problem. The book will show you how to transform data using the Query Editor and write functions in Power Query. A dedicated section will focus on functions such as IF, Index, and Modulo, and creating parameters to alter query paths in a table. You’ll also work with dashboards, get to grips with multi-dimensional reporting, and create automated reports. As you advance, you'll cover the M formula language in Power Query, delve into the basic M syntax, and write the M query language with the help of examples such as loading all library functions offline in Excel and Power BI. Finally, the book will demonstrate the difference between M and DAX and show how results are produced in M. </p><p>By the end of this book, you’ll be ready to create impressive dashboards and multi-dimensional reports in Power Query and turn data into valuable insights.</p>
Table of Contents (17 chapters)
Free Chapter
1
Section 1: Overview of Power Pivot and Power Query
6
Section 2: Power Query Data Transformations
11
Section 3: Learning M

Creating a calculated column

In this section, we will create a calculated column in Power BI Desktop to slice or filter a value or calculation on every row in a table. Let's run through the logic of what creating a calculated column means.

A calculated column is a new column that is added to an existing table. For each row of the table, the DAX formula is calculated immediately, just like using the autofill handle in Excel to fill in a formula. Be mindful of the fact that when using calculated columns, the result of the calculation is always stored in memory, unless of course it is reloaded or released when exiting or opening up Excel/Power BI. This will cause the table to be refreshed, which forces the column to recalculate. Let's see how this works:

  1. Open Power BI. For this example, we will be using the SSGThemePark.pbix file.
  2. You can create the DAX formula in any view, but I prefer the table view so that I can identify the data and see how the data is structured...