Hello, I am using MonetDB in a university project dealing with analysis of twitter data. "stuff" contains some pre-selected user ids. "tweets1207" contain tweet data for one day (userid, latitude, longitude, time, ....) What I want in the end is to find all (rounded) unique geo-coordinates of tweets by users in "stuff". I am using the following query: SELECT userid, ROUND(latitude,0) AS lat, ROUND(longitude,0) AS long FROM tweets1207 INNER JOIN stuff USING (userid) WHERE latitude <> 0 AND longitude <> 0 GROUP BY userid, lat, long ORDER BY userid, lat, long; The result set however still contains rows with duplicate values for "lat" and "long", e.g. userid lat long ----------------------------- 19703 41 -74 19703 41 -74 If I remove the INNER JOIN part from the query, the grouping works as expected. To check whether I am doing something fundamentally wrong (don't have much experience with SQL), I tried running the same query in a sqlite version of the data, where it produced the result I expected (although much, much slower...) Can anybody point me in the right direction? Am I doing something wrong here? Best regards and thanks in advance, Jonas