SELECT .. SELECT
The Derived Table (SELECT FROM SELECT)
You can use the results from one query in another query
You may use a SELECT statement in the FROM line.
In this case the derived table X has columns
The calculated values in the inner SELECT can be used in the outer SELECT.
SELECT name, ROUND(gdp_per_capita) FROM (SELECT name, gdp/population AS gdp_per_capita FROM bbc) X WHERE region='North America'
What about ties?
If one region has two countries with the same, highest population then the query will produce the right answers but there will be duplication- both countries will be shown.