For using DISTINCT keyword, you can use it like this:
SELECT DISTINCT
(SELECT min(ti.Country_id)
FROM tbl_countries ti
WHERE t.country_title = ti.country_title) As Country_id
, country_title
FROM
tbl_countries t
For using ROW_NUMBER(), you can use it like this:
SELECT
Country_id, country_title
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY country_title ORDER BY Country_id) As rn
FROM tbl_countries) t
WHERE rn = 1
Also with using LEFT JOIN, you can use this:
SELECT t1.Country_id, t1.country_title
FROM tbl_countries t1
LEFT OUTER JOIN
tbl_countries t2 ON t1.country_title = t2.country_title AND t1.Country_id > t2.Country_id
WHERE
t2.country_title IS NULL
And with using of EXISTS, you can try:
SELECT t1.Country_id, t1.country_title
FROM tbl_countries t1
WHERE
NOT EXISTS (SELECT 1
FROM tbl_countries t2
WHERE t1.country_title = t2.country_title AND t1.Country_id > t2.Country_id)