How do I use one SQL statement to invalidate groups of records?

I’m working on an assignment for class. I need to write an SQL statement that returns every single country in the database where no single ethnic group makes up more than 25% of the population. This is the closest I can get:

SELECT * FROM ethnicgroup WHERE percentage < 25;

But, that only returns records where ethnic groups are over 25% population. It doesn’t remove other rows in the table where a different ethnic group for the same country is under 25%.

The table looks like this (I limited the snippet below to 10 entires. It’s much, MUCH bigger.):

 country |    name    | percentage
---------+------------+------------
 AL      | Albanian   |         97
 AL      | Greek      |        0.9
 AL      | Macedonian |        0.9
 AL      | Roma       |        0.3
 AL      | Aromanian  |        0.3
 GR      | Greek      |         91
 GR      | Albanian   |        4.4
 GR      | Roma       |          2
 GR      | Macedonian |        1.5
 GR      | Turkish    |          1

Answer

I think you are looking for this

SELECT country FROM ethnicgroup 
GROUP BY country 
HAVING MAX(percentage)<25