Código PHP:
SELECT DISTINCT schools2.country, country_name_en
FROM schools2, countries
WHERE schools2.country = countries.country_code
AND schools2.ci != 0
ORDER BY country_name_en,$con
Código PHP:
SELECT schools2.country, countries.country_name_en
FROM schools2 INNER JOIN countries ON schools2.ID_country=countries.id
WHERE schools2.ci != 0 GROUP BY schools2.ID_country
ORDER BY countries.country_name_en,$con
Muchas gracias.