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Foundations: spreadsheets, data literacy and first SQL · Novice · Lesson 8 of 99 · 12 min video, then about 3 hours of practice
Cleaning messy data in a spreadsheet with Power Query
After this you can import a messy file, fix types, split and trim columns, remove duplicates and record every step so the cleaning can be rerun.
Why it matters
Real data arrives with trailing spaces, numbers stored as text, merged headers and duplicate rows. Power Query (built into Excel) records each cleaning step so you can refresh it next month instead of redoing it by hand, which is the first taste of reproducible analysis. The trap is cleaning by hand in the original sheet: it is fast once and impossible to audit or repeat.
How to use this resource
A practical demonstration of why Power Query beats manual cleaning, with the most common transformations.