Check this updated Fiddle of yours: http://sqlfiddle.com/#!2/0ca23/4
SELECT temp.*
FROM temp
JOIN
(SELECT `Country`, `City`, `Resource`, MAX(`Volume`) AS MaxVol
FROM `temp`
GROUP BY `Country`, `City`, `Resource`) t
ON temp.country = t.country
AND temp.city = t.city
AND temp.resource = t.resource
AND temp.volume = t.MaxVol
This query is basically making a INNER JOIN of your main table with the subquery which gets the max(volume) records for each country, city, and resource. The subquery results are aliased as table t
.