Power Query in Power BI: Clean Data and Create Date Columns

Power BI lesson 3

Power Query is the preparation step between a source file and a report. Cleaning once in the query is safer than manually fixing every visual.

Open Power Query

Select Home > Transform data. The Query Settings pane records each transformation as an Applied Step.

Simple cleanup sequence

1. Remove blank rows and columns.
2. Promote the first row to headers when needed.
3. Rename unclear columns.
4. Set Date, Whole number, Decimal number and Text types deliberately.
5. Remove duplicates only when you know what makes a row unique.
6. Close & Apply to load the clean result.

Useful date columns

Select a date column and use Add Column > Date to create Year, Month or Day Name. Date parts help you group a chart, but keep the original date as well.

Why steps matter

Power Query repeats the steps when the source is refreshed. That makes the process explainable and reduces manual mistakes.

Practice

Create a messy copy of SalesPractice with a blank row, a duplicate, and an Amount stored as text. Clean it, rename the query SalesClean, and verify the final types.

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