Window functions SQL - course 900 rub. from Stepik, training 10 hours, Date: December 2, 2023.

There is no section of SQL more misleading than "window functions". When you hear these words, you think “probably they just came up with some additional functions.” But no! “Window functions” are a separate language built into regular SQL. And it is more complex than everything you knew about selects combined.
In short, window functions help you create cool analytical reports without the use of Excel. Do you want to calculate the percentage of sales by month from total sales for the year? Window functions. Divide marketing channels into effective and ineffective? Window functions. Select the top 10 clients for each segment? They too.
What is the course about?
I've read dozens of "beginner" articles that explain what window functions are. They all suffered from one of two problems:
 Everything is clear, but 1% of the “windows” capabilities are described.
 It is written in such a complex way that if I did not already know the subject of discussion, I would not understand anything.
This is how this course was born - a clear and visual introduction to window functions. Understandable, because I can write clearly about complex topics. Visual - because I have prepared a hundred pictures and gifs that will help you understand the basic principles of “windows”.

Window functions are a really complex topic. Therefore, the course does not try to embrace the immensity, and gives that minimum of theory that brings 80% of the value. There is also a lot of practice on the course - because only with it will abstract knowledge turn into skills.
For whom
 For everyone who is confident in writing regular selects and wants to understand window functions.
 For analysts who are tired of “finishing up” raw reports in Excel.
 For programmers who would rather write one query than two pages of code.
 For people who like SQL.
The course is not suitable if you don't know SQL at all.
Cost and participation
The course consists of four modules. These are 15 lessons and 39 practical tasks. If you score 80% of points, you will receive a certificate, 90% of points will receive a certificate with honors.
The cost of the course is 500 ₽. The first module is available for free.