Rails: Has many through associations -- find with AND condition, not OR condition - sql

Question

I have the following query method in my ActiveRecord model:
def self.tagged_with( string )
array = string.split(',').map{ |s| s.lstrip }
select('distinct photos.*').joins(:tags).where('tags.name' => array )
end
So, this finds all records that have tags taken from a comma separated list and converted into an array.
Currently this matches records with ANY matching tags -- how can I make it work where it matches ALL tags.
IE: if currently if I input: "blue, red" then I get all records tagged with blue OR red.
I want to match all records tagged with blue AND red.
Suggestions?
-- EDIT --
My models are like so:
class Photo < ActiveRecord::Base
...
has_many :taggings, :dependent => :destroy
has_many :tags, :through => :taggings
...
def self.tagged_with( string )
array = string.split(',').map{ |s| s.lstrip }
select('distinct photos.*').joins(:tags).where('tags.name' => array )
end
...
end
class Tag < ActiveRecord::Base
has_many :taggings, :dependent => :destroy
has_many :photos, :through => :taggings
end
class Tagging < ActiveRecord::Base
belongs_to :photo
belongs_to :tag
end
A tag has two attributes: ID and Name (string).

Answer 1

This should work:
def self.tagged_with( string )
array = string.split(',').map{ |s| s.lstrip }
select('distinct photos.*').
joins(:tags).
where('tags.name' => array).
group("photos.id").
having("count(*) = #{array.size}")
end
Above will match photos that have tags red and blue at least. So that means if a photo has red, blue and green tags, that photo would match too.

Answer 2

You could change your select statement to the following:
select('distinct photos.*').joins(:tags).where('tags.name = ?', array.join(' OR '))
Which will properly create the OR string in the where clause.
ian.

Answer 3

LOL the solution for this is not a simple task--I thought through it from a SQL standpoint and it was UGLY. I figured somebody else has to have tried this so I did some searching and found this post that should help you:
HABTM finds with "AND" joins, NOT "OR"