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Exercise

Subquery inside SELECT

As explored in the video, there are often multiple ways to produce the same result in SQL. You saw that subqueries can provide an alternative to joins to obtain the same result.

In this exercise, you'll go further in exploring how some queries can be written using either a join or a subquery.

In Step 1, you'll begin with a LEFT JOIN combined with a GROUP BY to obtain summarized information from two tables in order to select the nine countries with the most cities appearing in the cities table. In Step 2, you'll write a query that returns the same result as the join, but leveraging a nested query instead.

Instructions 1/2
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  • 1
  • 2
  • Write a LEFT JOIN on the countries and cities tables to select names of countries in cities (aliasing country name as country), followed by counts of cities as cities_num.
  • Sort by cities_num (descending) and limit to the first nine records.
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