I say grouping, you say …
In this lesson we’ll review the aggregate functions we’ve used in the course:
COUNT() function counts all records in the aggregated group:
SELECT country, COUNT(*) AS users_count FROM users GROUP BY 1 ORDER BY 2 DESC
To count records only once we can add
SELECT product_id, COUNT(DISTINCT(user_id)) AS customers_total FROM purchases GROUP BY 1 ORDER BY 2 DESC
If we need something more advanced we can use if/else logic:
SELECT COUNT(CASE WHEN age > 65 THEN id END) AS seniors_count...
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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.