ruby-on-rails - Rails, Postgres, Distinct on and order by another column

Question

我在使用 PostgresDISTINCT ON方法订购时遇到了一些麻烦。以下仍然订购，unit_no我希望订购site_name。

@station = Station.select('DISTINCT ON(unit_no) unit_no, site_name, lat, long').
                   order('unit_no, site_name')

标签： ruby-on-railsruby-on-rails-5

Answer 1

如果您只想为site_name订购，则不需要添加“unit_no”

@station = Station.select('DISTINCT ON(unit_no) unit_no, site_name, lat, long').
               order('site_name')