aggregation option for virtual joins

[hogi]

☐ cool new feature
☐ could help many users!

☐ removes a „bug“

☑ nice to have

☐ nobody needs it

other wishes submitted by  

The idea:

if there is no unique identifier for virtual join -- add the possibility to define an aggregation to generate unique values.

• no need to have a unique identifier for virtual joins anymore
• a default option for data aggregation ["median" would be cool, but just works for numbers; so the not so useful "N"?]
  + a possibility to define the aggregation individually for each column (like in the query builder)

the benefit:

• the aggregation option makes the virtual join much more versatile
• the virtual join is almost as "dynamic" as the link functionality of summary table (<->  Query Builder)
• virtual links survive after the data is saved and re-opened (<-> link table)

the disadvantage:

the aggregation will slow down the virtal join.

the woraround:

• aggregation via summary table
• join via virtual link
• important: save as a script
  (to establish the dynamic link again after it got lost after saving the file)

[hogi]

@Sarah-Sylvestre 

this functionality could help a lot to improve the usability of virtual joins.
(I admit: definitely not at the same speed that we enjoy without aggregation)

[Sarah-Sylvestre]

Thank you for all the information @hogi! Your request has been captured and will be prioritized.