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<p>Hi Stefan,</p>
<p>I got it work with "aggregate()" not with "relation_aggregate()"</p>
<p>Not sure if relation_aggregate() works in both directions?</p>
<p>I also got a warning "The generated relations for a polymorphic relation cannot be used" ...</p>
<p>I have inheritance in my data model - maybe that is the cause that relation_aggregate() doesn't work, while aggregate works.</p>
<p>------------</p>
<p>Here is what works for me:</p>
<p><span style="font-family: courier new, courier, monospace;">with_variable(</span><br /><span style="font-family: courier new, courier, monospace;"> 'vereinbarung',</span><br /><span style="font-family: courier new, courier, monospace;"> get_feature(</span><br /><span style="font-family: courier new, courier, monospace;"> 'Vereinbarung',</span><br /><span style="font-family: courier new, courier, monospace;"> 't_id',</span><br /><span style="font-family: courier new, courier, monospace;"> vereinbarung</span><br /><span style="font-family: courier new, courier, monospace;"> ),</span><br /><span style="font-family: courier new, courier, monospace;"> aggregate(</span><br /><span style="font-family: courier new, courier, monospace;"> layer:='Vereinbarung',</span><br /><span style="font-family: courier new, courier, monospace;"> aggregate:='array_agg',</span><br /><span style="font-family: courier new, courier, monospace;"> expression:=@id,</span><br /><span style="font-family: courier new, courier, monospace;"> filter:=t_id = attribute(@vereinbarung,'t_id')</span><br /><span style="font-family: courier new, courier, monospace;"> )[0]</span><br /><span style="font-family: courier new, courier, monospace;">)</span></p>
<p>'Vereinbarung' is a geometry layer in my project that is related to a no-geometry table from which I want to trigger an atlas rendering ...</p>
<p>It is a pity that a "feature" doesn't contain it's internal ID in the attributes ... it would make it much easier! No silly workarounds with aggregates to get access to an internal id ...</p>
<p>Thanks a lot for the idea with the aggregates!</p>
<p>Andreas</p>
<p><br /></p>
<p id="reply-intro">On 2022-11-29 16:54, Stefan Giese (WhereGroup) via QGIS-Developer wrote:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
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<p>Hi Andreas,</p>
<p>in case of a relation 1:many you can use the <em>relation_aggregate</em> function, something like:</p>
<p><em> relation_aggregate('test_n_318_fk_test1_7993_id','concatenate',</em><em> to_string(@id),',')</em></p>
<div class="v1moz-cite-prefix">where the first parameter is the ID of the relation.</div>
<div class="v1moz-cite-prefix"> </div>
<div class="v1moz-cite-prefix">Hope this helps...</div>
<div class="v1moz-cite-prefix">Stefan</div>
<div class="v1moz-cite-prefix"> </div>
<div class="v1moz-cite-prefix">Am 29.11.2022 um 15:05 schrieb Andreas Neumann via QGIS-Developer:</div>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<p>Hi,</p>
<p>I am looking for a way to find out the internal id of a related layer with a QGIS expression.</p>
<p>@id and $id only work directly on the feature of the source layer, but not on related layers.</p>
<p>attributes(<br /> get_feature(<br /> 'Other Related Layer',<br /> 't_id',<br /> fkey_value<br /> )<br />)</p>
<p>doesn't contain the internal id of the other layer ...</p>
<p>Any ideas how to get access to internal ids of other layers?</p>
<p>Thank you and greetings,</p>
<p>Andreas</p>
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