[Qgis-user] relation reference filter

[Vedran Stojnović]

Hi,
I don't have much time to reproduce your set up, but please consult these
two videos and I'm sure that you'll be able to solve your problem and find
answer:
https://www.youtube.com/watch?v=-hunumayu2o
https://www.youtube.com/watch?v=lofFvzxDXNU


pet, 25. tra 2025. u 10:36 Kosza Antal <kosza.antal at gmail.com> napisao je:

> The settings are fine, the values work correctly in a dropdown list, what
> doesn't work is the filtering based on the value selected in the previous
> field.
> It's as if current_value() doesn't return a value.
>
>
> Vedran Stojnović <phidrho at gmail.com> ezt írta (időpont: 2025. ápr. 25.,
> P, 8:43):
>
>> Did you set up relational widgets properly?
>>
>> There is a good tutorial in the official docs:
>>
>> https://docs.qgis.org/3.40/en/docs/user_manual/working_with_vector/joins_relations.html#many-to-many-n-m-relations
>>
>> čet, 24. tra 2025. u 22:05 Kosza Antal via QGIS-User <
>> qgis-user at lists.osgeo.org> napisao je:
>>
>>>
>>> chris hermansen <clhermansen at gmail.com> ezt írta (időpont: 2025. ápr.
>>> 24., Cs, 20:07):
>>>
>>>> Kosza and list,
>>>>
>>>> On Thu, Apr 24, 2025 at 3:34 AM Kosza Antal via QGIS-User <
>>>> qgis-user at lists.osgeo.org> wrote:
>>>>
>>>>> Hello everyone,
>>>>>
>>>>> I want to implement the following in qgis
>>>>>
>>>>> Given 3 geopackage tables, one is the findings, the second is the
>>>>> type, the third is the material, and the fourth is the findings_material.
>>>>> The latter is a connecting table between the type and the material. The
>>>>> tables refer to each other with foreign keys. The foreign key is of type
>>>>> uuid.
>>>>>
>>>>> The task: in qgis, the findings table needs to be edited, the findings
>>>>> field refers to the type uuid with a foreign key, the material field refers
>>>>> to the uuid key of the material table. qgis automatically recognizes the
>>>>> relationships and sets up a relation reference widget.
>>>>>
>>>>> What I want: when I select the finding, i.e. the corresponding value
>>>>> from the type table, in the material it should filter the values based on
>>>>> the pivot table.
>>>>> This is how it looks in sql.
>>>>>
>>>>> SELECT
>>>>> a.uuid AS material_uuid,
>>>>> a.values AS material_values
>>>>> FROM
>>>>> material AS a
>>>>> JOIN
>>>>> result_material AS pivot ON a.uuid = pivot.material_fk
>>>>> WHERE
>>>>> pivot.characteristic_fk = '6c5356d0-3257-49ed-8f95-4262d33175c9';
>>>>>
>>>>> Just wondering if you could create a view based on your SELECT
>>>> statement that is editable (I've not done this in SQLite so I have no idea
>>>> if it's possible).
>>>>
>>>> Looking at your SQL vs your description, I'm not following.  You say
>>>> "the findings table needs to be edited"... Then it seems to me you need a
>>>> SELECT statement like this:
>>>>
>>>> SELECT f.*,t.*,m.*
>>>> FROM findings AS f
>>>> JOIN type AS t ON f.type_uuid = t.uuid
>>>> JOIN material AS m ON f.material_uuid = m.uuid
>>>>
>>>> I don't understand the purpose of the table you call
>>>> "findings_material" in one place and "result_material" in another and which
>>>> you say is "a connecting table between the type and the material".  It
>>>> seems to me the findings table connects type and material (as per my SELECT
>>>> statement).  Are you using it to restrict the combinations of type and
>>>> material?  If that's the case, then you should probably relate the findings
>>>> table to that restricting table rather than type and material directly.  I
>>>> would probably choose to call that restricting table something like
>>>> "allowed_type_material" and have a field on findings that was called
>>>> "allowed_type_material_uuid".
>>>>
>>>> Sorry that I'm not finding your problem description clear; I hope my
>>>> comments don't add confusion.
>>>>
>>>>
>>>>
>>>> --
>>>> Chris Hermansen · clhermansen "at" gmail "dot" com
>>>>
>>>> C'est ma façon de parler.
>>>>
>>>
>>> Sorry, I really worded it confusingly, the table names are in Hungarian,
>>> I overlooked something, let me clarify
>>>
>>> The main table is the findings, in which the "type" column is a foreign
>>> key to the "uuid" column of the types table, the material column is a
>>> foreign key to the "uuid" column of the material table
>>> 1. table - findings
>>> 2. table - types
>>> 3. table - material
>>> 4. table - findings material (connecting table), N:M relationship
>>>
>>> The sql query:
>>>
>>> SELECT
>>> a.uuid AS material_uuid,
>>> a.values AS material_value
>>> FROM
>>> material AS a
>>> JOIN
>>> findings_material AS pivot ON a.uuid = pivot.material_fk
>>> WHERE
>>> pivot.types_fk = '6c5356d0-3257-49ed-8f95-4262d33175c9';
>>>
>>> All this is being done for a qfield project,.
>>>
>>> I would like to solve the result of this sql query during data
>>> collection, that is, I create a point with gps, select the type of the
>>> find, and in the material column, only those values are displayed that are
>>> assigned to this type in the connection table.
>>> _______________________________________________
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>>>
>>
>>
>> --
>> Srdačan pozdrav / Kind regards,
>> Vedran Stojnović.
>>
>

-- 
Srdačan pozdrav / Kind regards,
Vedran Stojnović.
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