This advanced SQL exercise is part of the book: Advanced SQL – Practical Techniques and Use-Cases, which includes 100 day-to-day SQL challenges (and solutions), need-to-know advanced features, and key concepts.

An online gaming company uses the following table to store its customers’ passwords. As seen here, some of the customers chose to use a password composed of strings and numbers, while others chose to use a password composed exclusively by numbers.

CREATE TABLE passwords (id varchar(25))    


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