Question

I have the following call in my RoR script:

Foo.where("event = 'Login'").group('user_id').order('user_id ASC').count()

This gives me a list of all users and how much they have logged in in the form of:

<userid1> => <count>, <userid2> => <count>, ...}

This is great and very close to what I wan but I’ve been unable to convince it to sort by the count of logins instead, what I’d really like to have it do. There is also a column that has some info about the login session in the form of a character delimited string. I’d like to get at certain parts of that information.

To achieve this I’ve tried using find_by_sql and when I make the following call:

Foo.find_by_sql("SELECT userid, COUNT(*) AS number, SUBSTRING_INDEX(stuff, ',', 1) AS info FROM <table> WHERE event = 'Login' GROUP BY userid")

What I get is a ilst of Foo entries that contain the userids but not the count or the info. When I run this in the MySQL workbench it works like a charm. Is there something else I need to do to get this to work? Also, would there be a way to just do this using Foo.select or Foo.where? Thanks.

Update I have also tried this format, as demonstrated here:

Foo.find(:all, :select => 'count(*) count, userid', :group =>'userid')

But this too merely responds with the userids and does not spit out the count.

Update 2 Looking at the output a bit more i can see now that when i do the find_by_fql call everything is being found in the correct way and even being sorted. It just isn’t actually selecting the COUNT(*) or the SUBSTRING_INDEX.

Update 3 I also tried out this SO tip but when I tell it:

Foo.find(:all, :select => 'userid, count(*) as cnt', :group => 'userid')

It doesn’t print or find anything related to the var cnt. I’m totally baffled here because I’ve seen more than one example now that does it this ^^ way and I’ve yet to get it to succeed.

Answer 1

Actually, your problem is not an SQL problem. To generate the correct SQL you would just need this:

Foo.where("event = 'Login'").group('user_id').order('count_all').count()

Take a look in your log and you’ll find that this generates the following SQL:

SELECT COUNT(*) AS count_all, user_id AS school_id FROM `foos` GROUP BY user_id ORDER BY count_all

…and if you run that in your SQL console you’ll get what you want.

The problem is that Rails doesn’t return them in this order, Rails always returns these special group/count results in the order of the GROUP BY field. So, if you want them in a different order then you’ll need to do it in Ruby after getting the hash back.