rails 4 select distinct on multiple columns in postgres with where and limit

Question

How do you select multiple fields with distinct values, and other non-distinct fields with them, all in one call with where and limit? I tried .pluck (which supports multiple fields in rails 4), .uniq (which didn't work in my case).

Ryan · Accepted Answer · 2014-10-15 22:07:18Z

22

This is what worked for me, when used in the controller action

@models = Model.select('DISTINCT ON (field1,field2,field3) *')
     .where(id: params[:id])
     .limit(100)

answered Oct 15, 2014 at 22:07

Ryan

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VAD · Accepted Answer · 2020-11-04 14:58:59Z

0

Here's a bit less verbose and more ActiveRecord-centered approach which should work not only for Postgres but for MySQL as well.

Model.select('field1,field2').distinct.where(field3: 'value').limit(10)

answered Nov 4, 2020 at 14:58

VAD

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