I'm building a search for and got stuck on a cross-database references error
activities = Activity.order(:name).includes([:profile => :country])
activities = activities.where("lower(activities.city) like ?", "%#{params[:activity_search][:city].downcase}%") unless params[:activity_search][:city] == ""
activities = activities.where("activities.sport_id =?", params[:activity_search][:sport_id])
I'm trying to add something like this:
activities = activities.where("activities.profiles.country.id =?", params[:activity_search][:country_id])
an activity's country is the same as the activity creator's country.
How can I add this constraint in my query?
Thanks for your help
You need to use joins here to include the associations:
activities.joins(profiles: :country).where('countries.id = ?', params[:whatever])
This assumes Activity has_many :profiles and Profile has_one :country and countries is your table name, but I think all that is true based on your post. This will include the associated profiles and country with activities and allow you to use their attributes in the where method call.
Related
I need to create a live chat app and now I have three models :
ChatRoom
ChatRoomMember
ChatRoomMessage
From this three models, I use includes and references to get the list of chat_rooms for current login user. Here is the code that I have wrote.
#chat_rooms = ChatRoom.includes(:members).references(:members)
#chat_rooms = #chat_rooms.includes(:messages).references(:messages)
#chat_rooms = #chat_rooms.where 'chat_room_members.user_id = ?', #current_user.id
#chat_rooms = #chat_rooms.order 'chat_room_messages.created_at DESC'
#chat_rooms = #chat_rooms.limit(limit).offset(offset)
However, the order didn't work as I expected. What I want is that the chat_rooms are sorted by created_at column from the last message in that room. How can I do this ?
Here is the database structure :
Use association to avoid where 'chat_room_members.user_id = ?', #current_user.id
Here is my suggestion, assuming User has associations looking like:
class User
has_many :chat_room_members
has_many :chat_rooms, through: :chat_room_members
end
# list only rooms with at least on message
#chat_rooms = #current_user.chat_rooms.joins(:messages).order('chat_room_messages.created_at DESC').limit(limit).offset(offset)
# list all rooms even if there is no message attached
#chat_rooms = #current_user.chat_rooms.distinct.left_joins(:messages).order('chat_room_messages.created_at DESC').limit(limit).offset(offset)
Try this:
ChatRoom.includes(:messages).order('chat_room_messages.created_at DESC')
Thanks for everyone has help me to solve this probel. I have my own answer. Here is it.
SELECT chat_rooms.*, (SELECT chat_room_messages.created_at FROM chat_room_messages WHERE chat_room_messages.chat_room_id = chat_rooms.id ORDER BY chat_room_messages.id DESC LIMIT 1) AS last_message_at FROM chat_rooms INNER JOIN chat_room_members ON chat_room_members.chat_room_id = chat_rooms.id WHERE chat_room_members.user_id = #{#current_user.id} ORDER BY last_message_at DESC
I use raw query for solve this problem. Hope this can help anyone who need it !
I have 2 models in my Rails 3 app which I use to describe people and where they live
Unfortunately I set these up without using associations
The 2 tables are setup like this
People
id
name
location_id
Locations
id
name
what I want to do is list all entries in the Peoples table ordered by Locations.name alphabetically and People.name alphabetically
I can do a simple sort using this code which groups each person by a location but I need to drill into the Locations table as well
#people = People.all(:order => '"location_id" ASC, "name" ASC')
Anyone have any idea?
Also is it a good idea to set up an association in the People class to say location_id is Locations.id
Add
belongs_to :location
To the People class
Then you can query the following way:
#people = People.joins(:location).order("locations.name ASC, people.name ASC")
I want to build a rails request with 2 models.
I think it's quite simple, but I don't want to do a loop myself.
I'm in my country model:
def self.find_for_user(user_id)
wines = Wine.where("user_id = ?", user_id).group(:country_id)
where("countries.id IN ?", wines.map())
end
I want to get all countries depending the first request (the wines grouped by countries, I just need the countries)
I think I can do this in a single line where I put map() or another instruction. I just need to get all country_id fields for wines.
Thanks.
Assuming that you've got an association set up between wines and country (ie. has_many :wines in country.rb), I think this is what you're looking for:
def self.find_for_user(user_id)
joins(:wines).where('wines.user_id = ?', user_id).uniq
end
If all you want is all countries that have wine for a specific user, you can do that in SQL:
where("countries.id in (select country_id from wines where wines.user_id = ?)", user_id)
I'm having real trouble pulling out a set of records that are self-referentially related to a user in order to show these on a user's 'show' page.
Here's the idea:
Users (current_user) rate the compatibility between two other users (user_a and user_b). They can rate compatibility either positively or negatively: rating two users "compatible" creates a positive_connection between user_a and user_b, and rating them "incompatible" creates a negative_connection. So there are models for positive_connection, negative_connection and user.
Now I need to display only users that are overall_positively_connected_to(#user) (i.e. where positive_connections_to(#user).count > negative_connections_to(#user).count).
This is where I've got to, but I can't get any further:
User model:
def overall_positive_connected_to(user)
positive_connections_to(user).count > negative_connections_to(user).count
end
def positive_connections_to(user)
positive_connections.where("user_b_id = ?", user)
end
def negative_connections_to(user)
negative_connections.where("user_b_id = ?", user)
end
Controller
#user.user_bs.each do |user_b|
if user_b.overall_pos_connected_to(#user)
#compatibles = user_b
end
end
The code in the controller is clearly wrong, but how should I go about doing this? I'm completely new to rails (and sql), so may have done something naive.
Any help would be great.
So am I right in saying you have 3 models
User (id, name)
PositiveConnection (user_a_id, user_b_id)
NegativeConnection (user_a_id, user_b_id)
Or something of that sort.
I think you just want 2 models
and for convenience I'm going to rename the relations as "from_user" and "to_user"
User (id, name)
Connection (value:integer, from_user_id, to_user_id)
Where value is -1 for a negative
and +1 for a positive.
Now we can have do something like
(note: you need to sort out the exact syntax, like :foreign_key, and :source, and stuff)
class User
has_many :connections, :foreign_key => "from_user_id"
has_many :connected_users, :through => :connections, :source => :to_user
def positive_connections
connections.where(:value => 1)
end
def negative_connections
...
end
end
But we also now have a framework to create a complex sql query
(again you need to fill in the blanks... but something like)
class User
def positive_connected_users
connected_users.joins(:connections).group("from_user_id").having("SUM(connections.value) > 0")
end
end
this isn't quite going to work
but is kind of pseudo code for a real solution
(it might be better to think in pure sql terms)
SELECT users.* FROM users
INNER JOIN connections ON to_user_id = users.id
WHERE from_user_id = #{user.id}
HAVING SUM(connections.value) > 0
I have User and Album models with HABTM relationship
class Album < ActiveRecord::Base
has_and_belongs_to_many :users
class User < ActiveRecord::Base
has_and_belongs_to_many(:albums)
I'd like to find all the albums that are stored in the database but not associated with a particular user.
So far my code is like this:
Album.all(:order => "albums.created_at DESC", :include => "users", :limit => limit, :conditions => ["users.id != ? AND users.id IS NOT NULL", current_user.id])
but for some reason this is not working. It's returning albums that are associated with current_user.
here take a look at this ouptput from the console.
Check the users id i first fetch.
Then i fetch albums which should not have the users id
I then find one of the listed albums and ask it to return the associated users
one of those associated users is the one from above and shouldnt be there.
Can anyone help with the above?
I usually try to stay away sub-selects but I can't seem to get it to work any other way:
class Album < ActiveRecord::Base
scope :without_user, lambda{|u| where("#{quoted_table_name}.id NOT IN (SELECT `albums_users`.album_id FROM `albums_users` WHERE `albums_users`.user_id = ?)", u.id) }
end
user = User.find(30)
Album.without_user(user)
Assuming you created table albums_users to hold relationship data:
Album.includes(:users).
where(["albums_users.user_id IS NULL OR albums_users.user_id != ?", user_id])
I think it will generate SQL along the lines of
SELECT *
FROM albums LEFT OUTER JOIN albums_users ON albums.id = albums_users.album_id
WHERE albums_users.album_id IS NULL OR albums_users.album_id != #{user_id}
Try:
:conditions => ["users.id <> ? AND users.id IS NOT NULL", current_user.id]
A non-sql solution would be:
Album.all.reject{|album| user.albums.include?(album)}
Obviously, if you have tens of thousands of rows in your database, you might not want to do this.
Might do something like this, too:
Album.where(["id NOT IN (?)", user.albums_ids])
But if your users have a lot (say hundreds) of albums, you shouldn't do this either.
Just throwing in easy solutions if you're out for one of those.