Do tou have an error or result is not as expected ? If qgis complains about sql query or invalid layer, it can be because i forgot fields calculated through a function need to be explicitly named:
SELECT stationid, MAX(obs_date) AS max_date FROM your_layer GROUP BY stationid This should works on any valid layer. Tested successfully with a GeoJSON layer. Pierma Le 30 mars 2016 21:19, "Phil (The Geek) Wyatt" <[email protected]> a écrit : > Alas, this doesn't seem to work on the GEOJSON linked layer > > > > *From:* Pierre-Marie Le Dantec [mailto:[email protected]] > *Sent:* Wednesday, 30 March 2016 3:59 PM > *To:* Phil (The Geek) Wyatt > *Cc:* [email protected] > *Subject:* Re: [Qgis-user] Selecting records > > > > Hi Phil, > > For manipulating dates throught SQL you should use ISO format > ("YYYY-MM-DD"). > > Then, you can use a virtual layer with : > > SELECT stationid, MAX(obs_date) FROM your_layer GROUP BY stationid > > Cheers, > > Pierma > > > > 2016-03-30 13:09 GMT+11:00 Phil (The Geek) Wyatt <[email protected]>: > > I must be thick, but I can't get my head around this in QGIS > > > > Data > > stationid_ > > obs_date > > BK21 > > 28/03/2016 > > BK21 > > 29/03/2016 > > BK21 > > 30/03/2016 > > BL22 > > 28/03/2016 > > BL22 > > 29/03/2016 > > BL22 > > 30/03/2016 > > BL22 > > 31/03/2016 > > > > > > How do I select the Maximum date for each station ID? > > > > The data will be coming from a GEOJSON feed but I can also pull it as a > shape file if needs be > > > > > > Cheers - Phil > > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user > > > > > -- > > Pierre-Marie Le Dantec > > 73.64.34 >
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