[Qgis-user] How to create one new string-value from many other string-values?

[Bernd Vogelgesang]

On 23.09.20 10:21, Bernd Vogelgesang wrote:
>
> On 23.09.20 09:04, Jan.Rutha at STADT-KOELN.DE wrote:
>> hi there,
>> I got a table with a content for streetnames. For example the street
>> "Mainstreet" ist separated in
>> 10 different rows of data (one dataset for each letter in the word
>> "Mainstreet").
>>
>> I would like to merge these 10 datasets to one dataset. All those
>> datasets have one ID - so they qgis should
>> be able to search for the same Id and create a new textstring with
>> all the leters.
>>
>> I don't know how to practicly implement my idea in QGIS. Does anyone
>> have an idea for me?
>>
>> Thanks a lot and I wish you all a good day!
>>
>> Jan R.
>>
>>
> I think you could try to use an aggregate expression in the field
> calculator for a new field.
>
> sth like:
>
> aggregate(
>  layer:= 'streets',
>  aggregate:='concatenate',
>  expression:=name,
>  concatenator:='',  <- 2 single quotes, not 1 double, for an empty
> concatenator!
>  filter:= ID
>  )
>
> I don't know if the filter for ID works in this way. Can't check that
> cause I do not own such "interesting" data ;)
>
> Cheers,
>
> Bernd
>
>>
found no way to make my initial aproach work, but this:

  array_to_string(array_agg("street",group_by:="ID"),'','')

in the field calculator for a new text field glues together the complete
street name


If someone knows a resource with more examples how to work with all
these great functions available, please post it.


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