ActiveRecord and SELECT DISTINCT
I’m writing this post for two reasons:
- For some reason, I couldn’t find a lot of information on ActiveRecord and
SELECT DISTINCT(). - I’m hoping some Ruby / ActiveRecord guru will stumble across this and provide a better solution.
Recently, I was working on a project written in Ruby with ActiveRecord that required me to draw a list of host names from a database and perform some actions on them. The actions aren’t really important here. What I had a hard time finding was the ActiveRecord way of performing a SELECT DISTINCT() SQL query. My search came up empty, so I was forced to use the find_by_sql() method below. Obviously, I’ve changed the code to make it generic and not violate any non-disclosure agreements I might have.
records = Class.find_by_sql(["SELECT DISTINCT(hostname) FROM table"])This code works just fine, but it lacks a certain elegance. One thing that really bothers me is that I have to hardcode the table name into this line of code. If we make a change to the table name some time down the road, this line will have to be found and modified. Blech.
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November 20th, 2007 at 6:43 pm
Dude,
You can get away with something like this:
records = Class.find(:all, :select => “DISTINCT(hostname)”)
It’s a bit cleaner.
November 21st, 2007 at 1:49 am
Thanks for the heads up, Mando. I’ll give that a go.
January 31st, 2008 at 4:38 pm
Check out this page! I has a lot of good examples on how to do the subtle SQL stuff (like DISTINCT).
http://railsmanual.com/module/ActiveRecord::Calculations::ClassMethods
January 31st, 2008 at 4:43 pm
@Greg:
Thanks for the link. That’s a great resource.