case-then-when.sql

SELECT country_code, size
  CASE WHEN size > 50000000
    THEN 'large'
  WHEN size > 1000000
    THEN 'medium'
  ELSE 'small' END
  AS popsize_group
INTO pop_plus
FROM populations
WHERE year = 2015;

SELECT c.name, c.continent, c.geosize_group, popsize_group
FROM countries_plus AS c
  INNER JOIN pop_plus AS p
    ON c.code = p.country_code
ORDER BY geosize_group;