An SQL alert is an entry-level technique of anomaly detection. Anomaly detection is a whole world of different algorithms and it deserves a course of its own.
In this chapter, we’ve looked at a couple effective techniques to detect anomalies with a simple SQL query: comparing a number of events (errors/signups/etc) to 0 or its average value already tells us a lot about health of our systems. Remember 80/20 rule – most of the time it’s more than enough to start with SQL alerts for spotting critical problems in our processes and data.
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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. 