You can also restrict a GROUP BY query with a HAVING clause, which acts a lot like a where clause
SELECT country, COUNT()
FROM table
GROUP BY country
HAVING COUNT() > 100
Only countries having more than 100 rows would be returned.
This syntax can be used with a WHERE clause also.
SELECT country, COUNT()
FROM table
WHERE country LIKE 'UNITED%'
GROUP BY country
HAVING COUNT() > 100
Would return UNITED KINGDOM, UNITED STATES, etc., if the number of rows was more than 100