I'm trying to create a query based on an attribute of an associated record but am failing miserably
I've the following models:
class CompanyPay < ActiveRecord::Base
has_many :ee_pay
has_many :pay, :through => :ee_pay
end
class EePay < ActiveRecord::Base
belongs_to :company_pay
has_many :pay
end
class Pay < ActiveRecord::Base
belongs_to :ee_pay
has_one :company_pay, :through => :ee_pay
end
I'm trying to create a query that returns all Pay objects where the attribute apply_paye on their associated CompanyPay is true.
I've been trying to get my head around joins, scope, lambdas etc since yesterday but I'm just confusing myself more at the stage.
The query I want would be something like this but I just don't know how to phrase it properly
#records = Pay.where(employee_id: current_employee.id, {|p| p.company_pay.apply_paye == true}).order(:id)
Can anyone help me out. Can I write a one line query? Should I be using a join? Should a lambda be used?
Thanks for looking
Edit 1
I've edited the original post as I gave the wrong attribute name by mistake (should be apply_paye not taxable).
Tried the following query provided by fylooi
#records = Pay.joins(:ee_pay => :company_pay).where(:pay => {:employee_id => current_employee.id }, :company_pay => {:apply_paye => true})
But am getting the following error:
ActiveRecord::StatementInvalid in PayLinesController#update
PG::UndefinedTable: ERROR: missing FROM-clause entry for table "pay" LINE 1: ...any_pays"."id" = "ee_pays"."company_pay_id" WHERE "pay"."emp... ^ : SELECT "pays".* FROM "pays" INNER JOIN "ee_pays" ON "ee_pays"."id" = "pays"."ee_pay_id" INNER JOIN "company_pays" ON "company_pays"."id" = "ee_pays"."company_pay_id" WHERE "pay"."employee_id" = 1 AND "company_pay"."apply_paye" = 't' ORDER BY "pays"."id" ASC
Edit 2 - Solved
Pluralising the table names in the query worked, as per the suggestion from David Aldridge.
This is the final query:
#records = Pay.joins(:ee_pay => :company_pay).where(:pays => {:employee_id => current_employee.id }, :company_pays => {:apply_paye => true})
Thanks for your help
Something like this?
Pay.joins(:ee_pay => :company_pay).where(:company_pay => {:taxable => true})
Related
I'm trying to use active-record query possible connections between airports.
I described the models I created already in another question here:
n:m self-join with ruby on rails active record
Basically, what I can do now is that:
ny = Airport.create({"city" => "New York"})
la = Airport.create({"city" => "Los Angeles"})
ny.destinations << la
la.destinations << ny
I ran into an issue querying the data I'm looking for, which is quite simple in SQL but I had no luck with active record yet.
ny = Airport.where('city = ?', 'New York')
ny.destinations
returns the correct objects, but all of them.
The SQL query looks like that:
SELECT "airports".* FROM "airports" INNER JOIN "connections" ON "airports"."id" = "connections"."destination_id" WHERE "connections"."airport_id" = 3
I'd like to filter those results by cities starting with "s" for example, so an SQL query could look like that:
SELECT "airports".* FROM "airports" INNER JOIN "connections" ON "airports"."id" = "connections"."destination_id" WHERE "connections"."airport_id" = 3 AND airports"."city" LIKE "s%"
I tried it this way:
ny.destinations.where('city LIKE ?', '#{params[:query]}%')
But I always get an empty result.
How could I use active record to filter my resulting objetcs?
edit: Thats the best solution I found so far:
I added the cityLike() method to the Airport model:
app/models/airport.rb:
class Airport < ActiveRecord::Base
attr_accessible :city, :name
has_many :connections
has_many :destinations, :through => :connections
has_many :inverse_connections, :class_name => "Connection", :foreign_key => "destination_id"
has_many :inverse_destinations, :through => :inverse_connections, :source => :airport
def self.cityLike(query)
where("city LIKE ?", "%#{query}%")
end
end
app/model/connection.rb:
class Connection < ActiveRecord::Base
attr_accessible :destination_id, :airport_id
belongs_to :airport
belongs_to :destination, :class_name => "Airport"
end
Now I can query the objects with the following statement:
Airport.find(1).destinations.cityLike("a")
Not sure if it's the best solution, but it produces the query I was looking for.
Thanks a lot to all af you!
ActiveRecord::Base.execute(sql) lets you use pure SQL to do your query and returns the relevant model.
What about this?
Airport.find(:all, joins: "INNER JOIN `connections` ON airports.id = connections.destination_id").where("connections.airport_id = ? AND airports.city LIKE ?", ny_id, "s%")
This code:
ny.destinations.where('city LIKE ?', '#{params[:query]}%')
works like this--first you have an object ny repesenting the city of New York. When you say ".destinations" you have now followed a relation you defined in your model to retrieve all the destinations that you can get to from New York. However, if I'm imagining your database schema correctly, these destinations don't actually have a field called "city"; instead, they have a destination_id, which ties the destination to a particular airport, and it's the airport that has a city associated with it.
So when you query the destination table for 'city LIKE ?', it doesn't find any matching records.
Instead, try
ny.destinations.joins(:airports).where('city LIKE ?', '#{params[:query]}%')
I have such code
#pre_articles = Article.find(:all, :conditions => { :ART_ID => #linkla.map(&:LA_ART_ID)})
#articles = Kaminari.paginate_array(#pre_articles).page(params[:page]).per(15)
It's selecting for me array of data, but it's huge, so i decided to add pagination. It select's 15 entries for view, but also for every page (in log) i see, how sql is selecting all array as in first #pre_articles. For more speed: how to select on every page for example 0-15, 15-30, 30-45 etc entries and send it for view? now it's selecting all data, but dislpaying as i need
Oh sorry, important!:
#linkla = LinkArt.where(:LA_ID => #la_typs.map(&:LAT_LA_ID), :LA_GA_ID => #genart.map(&:GA_ID))
#articles = Article.where(:ART_ID => #linkla.map(&:LA_ART_ID)).page(params[:page]).per(15)
So looks my query. As you see depending on #linkla results i select articles, and link la is selecting many as before... how to do that he select only for my page
Solution to the stated problem:
LinkType
has_many :links
# let us assume there is a column called name
# I wasn't sure about this model from your description
GenArt
has_many :links
# let us assume there is a column called name
Link
belongs_to :article
belongs_to :link_type
belongs_to :gen_art
# columns: id, article_id, link_type_id, gen_art_id
Article
has_many :links
Assuming you the params hash contains link_type_names and gen_art_names
Article.joins(:links => [:link_type, :gen_art]).where(
:links => {
:link_type => {:name => params[:link_type_names]},
:link_type => {:name => params[:gen_art_names]}
}
).page(7).per(50)
What about using where clause instead of conditional find?
#articles = Article.where(:ART_ID: #linkla.map(&:LA_ART_ID)).page(params[:page]).per(15)
The SQL query generated will include a LIMIT clause to avoid loading unnecessary data.
Example
class User
has_many :tickets
end
I want to create association which contains logic of count tickets of user and use it in includes (user has_one ticket_count)
Users.includes(:tickets_count)
I tried
has_one :tickets_count, :select => "COUNT(*) as tickets_count,tickets.user_id " ,:class_name => 'Ticket', :group => "tickets.user_id", :readonly => true
User.includes(:tickets_count)
ArgumentError: Unknown key: group
In this case association query in include should use count with group by ...
How can I implement this using rails?
Update
I can't change table structure
I want AR generate 1 query for collection of users with includes
Update2
I know SQL an I know how to select this with joins, but my question is now like "How to get data" . My question is about building association which I can use in includes. Thanks
Update3
I tried create association created like user has_one ticket_count , but
looks like has_one doesn't support association extensions
has_one doesn't support :group option
has_one doesn't support finder_sql
Try this:
class User
has_one :tickets_count, :class_name => 'Ticket',
:select => "user_id, tickets_count",
:finder_sql => '
SELECT b.user_id, COUNT(*) tickets_count
FROM tickets b
WHERE b.user_id = #{id}
GROUP BY b.user_id
'
end
Edit:
It looks like the has_one association does not support the finder_sql option.
You can easily achieve what you want by using a combination of scope/class methods
class User < ActiveRecord::Base
def self.include_ticket_counts
joins(
%{
LEFT OUTER JOIN (
SELECT b.user_id, COUNT(*) tickets_count
FROM tickets b
GROUP BY b.user_id
) a ON a.user_id = users.id
}
).select("users.*, COALESCE(a.tickets_count, 0) AS tickets_count")
end
end
Now
User.include_ticket_counts.where(:id => [1,2,3]).each do |user|
p user.tickets_count
end
This solution has performance implications if you have millions of rows in the tickets table. You should consider filtering the JOIN result set by providing WHERE to the inner query.
You can simply use for a particular user:
user.tickets.count
Or if you want this value automatically cached by Rails.
Declare a counter_cache => true option in the other side of the association
class ticket
belongs_to :user, :counter_cache => true
end
You also need a column in you user table named tickets_count.
With this each time you add a new tickets to a user rails will update this column so when you ftech your user record you can simply accs this column to get the ticket count without additional query.
Not pretty, but it works:
users = User.joins("LEFT JOIN tickets ON users.id = tickets.user_id").select("users.*, count(tickets.id) as ticket_count").group("users.id")
users.first.ticket_count
What about adding a method in the User model that does the query?
You wouldn't be modifying the table structure, or you can't modify that either?
How about adding a subselect scope to ApplicationRecord:
scope :subselect,
lambda { |aggregate_fn, as:, from:|
query = self.klass
.select(aggregate_fn)
.from("#{self.table_name} _#{self.table_name}")
.where("_#{self.table_name}.id = #{self.table_name}.id")
.joins(from)
select("(#{query.to_sql}) AS #{as}")
}
Then, one might use the following query:
users = User.select('users.*').subselect('COUNT(*)', as: :tickets_count, from: :tickets)
users.first.ticket_count
# => 5
I am trying to get a list, and I will use books as an example.
class Book < ActiveRecord::Base
belongs_to :type
has_and_belongs_to_many :genres
end
class Genre < ActiveRecord::Base
has_and_belongs_to_many :books
end
So in this example I want to show a list of all Genres, but it the first column should be the type. So, if say a genre is "Space", the types could be "Non-fiction" and "Fiction", and it would show:
Type Genre
Fiction Space
Non-fiction Space
The Genre table has only "id", "name", and "description", the join table genres_books has "genre_id" and "book_id", and the Book table has "type_id" and "id". I am having trouble getting this to work however.
I know the sql code I would need which would be:
SELECT distinct genres.name, books.type_id FROM `genres` INNER JOIN genres_books ON genres.id = genres_books.genre_id INNER JOIN books ON genres_books.book_id = books.id order by genres.name
and I found I could do
#genre = Genre.all
#genre.each do |genre|
#type = genre.book.find(:all, :select => 'type_id', :group => 'type_id')
#type.each do |type|
and this would let me see the type along with each genre and print them out, but I couldn't really work with them all at once. I think what would be ideal is if at the Genre.all statement I could somehow group them there so I can keep the genre/type combinations together and work with them further down the road. I was trying to do something along the lines of:
#genres = Genre.find(:all, :include => :books, :select => 'DISTINCT genres.name, genres.description, books.product_id', :conditions => [Genre.book_id = :books.id, Book.genres.id = :genres.id] )
But at this point I am running around in circles and not getting anywhere. Do I need to be using has_many :through?
The following examples use your models, defined above. You should use scopes to push associations back into the model (alternately you can just define class methods on the model). This helps keep your record-fetching calls in check and helps you stick within the Law of Demeter.
Get a list of Books, eagerly loading each book's Type and Genres, without conditions:
def Book < ActiveRecord::Base
scope :with_types_and_genres, include(:type, :genres)
end
#books = Book.with_types_and_genres #=> [ * a bunch of book objects * ]
Once you have that, if I understand your goal, you can just do some in-Ruby grouping to corral your Books into the structure that you need to pass to your view.
#books_by_type = #books.group_by { |book| book.type }
# or the same line, more concisely
#books_by_type = #books.group_by &:type
#books_by_type.each_pair do |type, book|
puts "#{book.genre.name} by #{book.author} (#{type.name})"
end
I am using a join query to get the attributes of another table along with the query.
city = City.first(:select => "cities.*, states.name as state_name, states.time as state_time"
:joins => "LEFT JOIN states on cities.state_id = states.id",
:conditions => ["states.name = ?", params[:state]])
Here, the problem is that when I get the values from the joined tables like city.state_time, I will get the string like 2010-11-12 05:00:00 instead of the time object(no typecasting is done by Rails for these fields). It makes sense since I am calling City model and the methods used for typecasting time column will be in State model. I will have to explicitly parse time like this and will have to fight with the time zone issues as well. (as Rails do some customizations while giving the Time object and I will have to do these for these columns). Is there any way to link the columns to the State while doing the join. One method I thought of was like this.
state = State.new(:name => city.state_name, :time => city.state_time)
and use state.name and state.time. Is there a better way?
here's probably what you want:
class City < ActiveRecord::Base
belongs_to :state
end
class State < ActiveRecord::Base
has_many :cities
end
a = City.joins(:state).includes(:state).where(['states.name = ?', params[:state]]).first
a.state.time
This works using an inner join and has some conditions:
City must belong to only one state. If the city doesn't belong to any state the query won't return it because of the inner join
Rails 2 Syntax
a = City.find(:all, :conditions => ['states.name = ?', params[:state]], :joins => :state, :include => :state)