How to create all possible pairs of cities?

Question

SQL

Good afternoon! There is a table with city names. How to write a query that displays all the possible number of pairs that these cities can create with each other?

Answer 1

JOIN

Answer 2

If you are interested in combinations of n elements by k=2, then, for example, the cities table, in which city names are in city_name, the solution is
SELECT t1.city_name, t2.city_name FROM cities t1 CROSS JOIN cities t2 WHERE t1.city_name < t2. city_name;