163. Recap: percentages calculation

Calculating percentages or rates is fundamental to data analysis of any kind. We should feel it by heart, use it as easy as addition or subtraction.

I find the last exercise a perfect material to repeat all the ways we’ve learned so far to calculate percentages.

Percentage with CASE

We know that for every user record there’s at least one record in devices table. It allows us to calculate percentage of users with a certain device_type only based on devices table:

SELECT 100.0 * COUNT(DISTINCT(CASE WHEN device_type = 'iphone' THEN user_id END)) /...
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Anatoli Makarevich, author of SQL Habit About SQL Habit

Hi, it’s Anatoli, the author of SQL Habit. 👋

SQL Habit is a course (or, as some of the students say, “business simulator”). It’s based on a story of a fictional startup called Bindle. You’ll play a role of their Data Analyst 📊 and solve real-life challenges from Business, Marketing, and Product Management.

SQL Habit course is made of bite-sized lessons (you’re looking at one atm) and exercises. They always have a real-life setting and detailed explanations. You can immediately apply everything you’ve learned at work. 🚀

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-- Type your query here, for example this one -- lists all records from users table: SELECT * FROM users
LIMIT 500
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