Fan-out problem when joining to a view which might not have a primary key?

  • 8 June 2022
  • 0 replies

Hi sir, 

I’d like to ask a question. As someone use google big query, you might notice that quite often we don’t have a primary key in the table. 


I learnt from the Looker bootcamp saying in order to avoid fan-out problem, two conditions need to be fulfilled, one is that either side of the joined views all have declared their primary keys, and the other is to correctly specify their join relationship. 


But the challenge that I run into is that my view (let’s call it A view), during the process of creation, apply UNNEST() to some nested columns. And now I have another view (let’s call it B view) which has a primary key.


I wonder if I can just specify the primary key in that other view (B view), and join it to the A view which has not primary key specified. Would that still work and avoid fan-out problem?


Thanks for any feedback on this.  

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