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<p>Hi Brent,</p>
<p>The relations are a complicated topic and are being worked on. As you have discovered, they are also still a bit limited in what you can do with them until now. But I hope that is will change in the future.</p>
<p>I can summarize a bit what you can do with them now:</p>
<p>- embed linked/filtered tables in forms (I recommend you use it with the drag and drop forms and put them in separate tabs)</p>
<p>- you can add/delete features in related tables</p>
<p>- for n:m you can also link/unlink records in related tables</p>
<p>- for n:m there is a new mode now in 2.14 where you can hide the in-between link table</p>
<p>- in print composer in atlas context you can use it as a table source to create data-sheets</p>
<p>There may be more what you can do. I don't claim that my list is complete. And of course different organizations have different needs/requirements/ideas what they want to do with the relations.</p>
<p>Now what you want to do (select/filter features in a related table based on a selection in a related table) is not yet possible. I invite you to specify exactly what you want and join the relations effort to improve what you can do with relations in future QGIS versions.</p>
<p>My organization has plans to have aggregate functions implemented on related tables - things like count, sum, mean, min, max, concatenate, etc. - to be used in tables or in the print composer (atlas context).</p>
<p>Greetings,</p>
<p>Andreas</p>
<p>On 2016-02-24 02:16, Brent Wood wrote:</p>
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<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR">Firstly, thanks to those who already helped me with this.</div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR"> </div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR">I have established a relation between non-spatial catch records in a postgis table and a table of station information (linked via foreign key).</div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR"> </div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr">If I click on a station with the info tool, I can see the various catch records from that station - so the relation is working.</div>
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<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr">But that seems to be it. If I filter on the species in the catch, that only applies to the catch data showing up when I select a station - it does NOT hide stations where that species was not caught. I cannot change symbology based on a relation, I cannot select features based on a relation - all I can do is view the records - and with 70 fields in the station layer, the catch records are just a small window at the bottom of the form.</div>
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<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr">It seems that to be useful I need to create the view or table in the database & access this with QGIS - whioch has issues for users without create access in the database - which is most of them.</div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr"> </div>
<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr">Is work on this area (relations) of QGIS actively ongoing, or should I look for non-QGIS approaches?</div>
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<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr">Thanks,</div>
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<div id="yui_3_16_0_1_1455838277084_4051" class="qtdSeparateBR" dir="ltr"> Brent Wood</div>
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