[Qgis-user] Selecting records

[Phil (The Geek) Wyatt]

Brilliant - now works - Many thanks Pierma!

 

From: Pierre-Marie Le Dantec [mailto:pierremarie.ledantec at gmail.com] 
Sent: Thursday, 31 March 2016 7:17 AM
To: Phil (The Geek) Wyatt
Cc: Qgis-user at lists.osgeo.org
Subject: RE: [Qgis-user] Selecting records

 

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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