Ruby Postgresql Sort database table info by specific column's data in a loop

Question

I don't even know how to ask this correctly, so pardon me if my question is confusing. I have a Table called Colors -

I would like to iterate a list of all the colors in the table, but presorted by 'color-family' so the result would look something like this:

Colors:
   Reds -
      Maroon
      Stop Sign
   Yellows -
      Canary
   Blues - 
      Sky Blue
      Royal Blue
   Greens -
      Neon Green

But I have no idea the sql syntax to collect and sort that kind of information.
Surprisingly, this code didn't work ;)

<% @group = Colors.presort_by("color-family") %> 
<% @color = Colors.all %>
<% @group.each do |group| %>
  <%= group.color-family %>s - <br>
  <% if @[email protected] %>
  <%= @color.name %>
  <% end %>
 <% end %>

lol. As you can see, I have no real idea where to start. Any help would be greatly appreciated. I don't have any sql query experience whatsoever.

Thanks again!

@colors = Color.order(:color-family ,:name) something like this, depends what order you want. You could reference here — Weibo Chen
– Weibo Chen, Commented Dec 30, 2016 at 5:42

max pleaner · Accepted Answer · 2016-12-30 16:32:46Z

1

I'm not sure if there's a way to do this using just ActiveRecord query methods. But it can easily be done in-memory using Ruby's Enumerable#group_by, and the performance will be good unless it's a large data set (in which case you'd probably want to cache the results, or look into a more complex SQL query)

@colors = Color.all
grouped = @colors.group_by { |color| color.color_family }
# or             .group_by &:color_family

This will return a hash where keys are color family (strings) and values are arrays of Color records.

edited Dec 30, 2016 at 16:32

answered Dec 30, 2016 at 6:16

max pleaner

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