[Qgis-user] Selecting records

[Pierre-Marie Le Dantec]

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" <phil at wyatt-family.com> a
écrit :

> Alas, this doesn't seem to work on the GEOJSON linked layer
>
>
>
> *From:* Pierre-Marie Le Dantec [mailto:pierremarie.ledantec at gmail.com]
> *Sent:* Wednesday, 30 March 2016 3:59 PM
> *To:* Phil (The Geek) Wyatt
> *Cc:* Qgis-user at lists.osgeo.org
> *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 <phil at wyatt-family.com>:
>
> 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
>
>
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>
>
>
> --
>
> Pierre-Marie Le Dantec
>
> 73.64.34
>
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