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Editorial Team
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Asked: 2026-06-06T08:22:20+00:00

I have a relationship between two models, Registers and Competitions . I have a

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I have a relationship between two models, Registers and Competitions. I have a very complicated dynamic query that is being built and if the conditions are right I need to limit Registration records to only those where it’s Competition parent meets a certain criteria. In order to do this without select from the Competition table I was thinking of something along the lines of…

Register.where("competition_id in ?", Competition.where("...").collect {|i| i.id})

Which produces this SQL:

SELECT "registers".* FROM "registers" WHERE (competition_id in 1,2,3,4...)

I don’t think PostgreSQL liked the fact that the in parameters aren’t surrounded by parenthesis. How can I compare the Register foreign key to a list of competition ids?

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1 Answer

  1. Editorial Team

    you can make it a bit shorter and skip the collect (this worked for me in 3.2.3).

    Register.where(competition_id: Competition.where("..."))

    this will result in the following sql:

    SELECT "registers".* FROM "registers" WHERE "registers"."competition_id" IN (SELECT "competitions"."id" FROM "competitions" WHERE "...")
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