Chapter 2: Power Query Basics (Data Transformation)

Ishika January 23, 2026

Power Query Basics: Data Transformation Made Easy

Power Query is one of the most important components of Power BI. It is used to clean, transform, and prepare raw data before it is loaded into the Power BI data model.

In real-world business scenarios, data is rarely clean. Power Query helps convert unstructured and inconsistent data into a clean, reliable, and analysis-ready format.

4.1 What is Power Query?

Power Query is a data preparation tool that follows the ETL process:

ETL Stage	Explanation
Extract	Collecting data from sources like Excel, CSV, databases, or web
Transform	Cleaning, filtering, reshaping, and modifying the data
Load	Loading transformed data into Power BI

4.2 Opening Power Query Editor

Steps to open Power Query Editor:

Open Power BI Desktop
Go to Home → Transform Data
Power Query Editor window will open

Power Query Editor works separately from the report view and focuses only on data cleaning and preparation.

4.3 Power Query Editor Interface

Section	Purpose
Ribbon	Contains transformation tools such as Remove Rows, Split Column, Merge Queries
Queries Pane	Displays all tables (queries) loaded into Power BI
Data Preview	Shows a preview of the dataset
Query Settings	Shows properties and applied transformation steps

4.4 Applied Steps (Very Important)

Applied Steps record every transformation performed on the data. Each step is executed in sequence and can be edited or deleted.

Steps run from top to bottom
Power Query is non-destructive
Original source data remains unchanged

4.5 Common Data Cleaning Operations

Operation	Description
Remove Columns	Deletes unnecessary columns to improve performance
Remove Rows	Removes blank, top, or unwanted rows
Change Data Type	Ensures correct interpretation of data
Filter Rows	Keeps only relevant records