How we write these guides
Short, practical guides to comparing exports, sheets and lists. Here is who writes them, how they are checked and what they will never do.
Who writes them
The guides are written by Michal Piják, a data engineer and the maker of Calamo. They come from the same problem he solves at work: two exports of the same data and the question of what changed between them.
How they are checked
- The answer comes first. Each guide answers the question in the first paragraphs and then explains the details and edge cases.
- Every function and limit is checked against its documentation. Excel functions, version requirements and limits link to Microsoft's documentation; code links to the library's own docs. These links are listed under Sources at the end of each guide.
- We say when a method breaks. Wildcards, numbers stored as text, re-sorted rows and duplicate keys cause most wrong answers, so the guides point them out.
- Dates are visible. Each guide shows when it was published or last updated.
How Calamo is mentioned
We make Calamo, a free tool that compares two CSV files by key in the browser. Guides solve the problem without it first, and mention Calamo as one option where it fits. Where Excel, Power Query or a few lines of code are the better choice, the guide says so.
There are no sponsored posts and no affiliate links.
Illustrations
The header illustrations are AI-assisted and labelled as such. Diagrams are drawn by hand from the example in the text.
Corrections
Found a mistake or a formula that does not work in your version of Excel? Write to hello@calamo.io. Corrections are made in the guide and the date is updated.