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 education company manages a table that holds the details of the company’s customers. Each row in this table specifies: Serial number, customer name, city, and the date the customer joined the company.

CREATE TABLE customers
(c_id int identity(1,1),
c_name varchar(25),
city varchar(25),
join_date date)

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