SQL Window Functions Explained

Window functions are probably the most confusing section of SQL. You might think, “So what? They just came up with some additional functions”. Not really. “Window functions” is a separate language built into regular SQL. And it’s more complicated than everything you know about SELECTs.

In short, window functions assist in making great analytical reports without Excel. Maybe you want to calculate monthly sales percentages over the year? Window functions. Split marketing channels into effective and ineffective ones? Window functions. Choose the top 10 clients for each segment? Same.

I've read several dozen articles explaining SQL window functions. They all suffered from one of two problems:

  1. Easy read without much practical value, describing 10% of features.
  2. Difficult to comprehend. If I did not know the subject — I would not understand a thing.
How I see complex queries
SQL window queries can look like this for an unfamiliar reader.

I want people to understand SQL windows better. So I wrote a book — SQL Window Functions Explained.

About the book

It is a clear and visual introduction to window functions. Clear — because I can describe complex topics in a readable way. Visual — because I have prepared a hundred pictures and GIFs to help you understand SQL windows.

Window functions are a complex topic. So the book only teaches a little at a time. It gives just enough theory and a lot of practice — because it’s the only way to turn abstract knowledge into skills.

Here is what you will learn:

  1. Why use window functions
  2. Windows and functions
    • Ranking
    • Offset
    • Aggregation
    • Rolling aggregates
    • Statistics
  3. Frames
    • ROWS and GROUPS
    • RANGE
    • EXCLUDE
    • FILTER
  4. Practice
    • Product analytics
    • Clustering
Book poster
Every chapter covers a single topic in depth

To preview the first few chapters, visit the links in the table of contents above.

10 of the 13 chapters are ready, and I’ll publish the rest by May 2023. You can buy an early access release for $10.

Get the book

Follow @ohmypy on Twitter to keep up with new posts 🚀