arel

问题 the following code fieldvalue = Admin::FieldValue.where(:item_id => @admin_item.id, :field_id => key) fieldvalue.update_attributes(:value => value) raise the following error NoMethodError (undefined method `update_attributes' for #<ActiveRecord::Relation:0x00000102dfc868>): why is it a Relation object and not a FieldValue object, what's the right way to manage this 回答1: fieldvalue should return only one value? fieldvalue = Admin::FieldValue.where(:item_id => @admin_item.id, :field_id => key)

问题 I want to store IP addresses (v4 and v6) in my rails application. I have installed an extension to MySQL adds functions to convert ip strings to binary which will allow me to query by IP range easily. I can use unescaped sql statements for SELECT type queries, thats easy. The hard part is that I also need a way to overwrite the way the field is escaped for insert/update statements. This ActiveRecord statement new_ip = Ip.new new_ip.start = '1.2.3.4' new_ip.save Should generate the following

问题 Here is what I'm trying to do class Question has_many :votes end class Vote belongs_to :question end I want to find all questions ordered by the number of votes they have. I want to express this in Arel (in Rails 3) without using any counter caches. Is there any way of doing this ? Thanks. 回答1: Try this: Question.select("questions.*, a.vote_count AS vote_count"). joins("LEFT OUTER JOIN ( SELECT b.question_id, COUNT(b.id) AS vote_count FROM votes b GROUP BY b.question_id ) a ON a.question_id =

问题 I have a scope defined as follows: scope :ignore_unavailable, lambda { where([ "Item.id NOT IN (SELECT id FROM Cars WHERE Cars.status = 'NA'" ]) } Currently its using hardcoded tables names. How can I improve it using frameworks like Arel ? Will appreciate any help here. I am on Rails 3.2 回答1: If you are using rails 4, one way would be scope :ignore_unavailable, lambda { where.not(id: Car.where(:status => "NA").pluck(:id)) } For rails 3 scope :ignore_unavailable, lambda { where("id not in (?)

问题 I have a scope defined as follows: scope :ignore_unavailable, lambda { where([ "Item.id NOT IN (SELECT id FROM Cars WHERE Cars.status = 'NA'" ]) } Currently its using hardcoded tables names. How can I improve it using frameworks like Arel ? Will appreciate any help here. I am on Rails 3.2 回答1: If you are using rails 4, one way would be scope :ignore_unavailable, lambda { where.not(id: Car.where(:status => "NA").pluck(:id)) } For rails 3 scope :ignore_unavailable, lambda { where("id not in (?)

问题 I want to find courses which have at least 1 variant with variant_type = 1 and don't have any variant with variant_type = 2. So my query like: Course.where("id IN ( SELECT course_id FROM course_variants WHERE variant_type = 1 ) AND id NOT IN ( SELECT course_id FROM course_variants WHERE variant_type = 2 )") Additionally, a course has many course_variants . I'm using a raw query in where clause, I want to improve this using Active record interface or Arel, any solution for this? Thank you!

问题 So Rails doesn't have support for :through associations through a habtm relationship. There are plugins out there that will add this in for Rails 2.x, but I'm using Rails 3 / Edge, and only need the association for one particular model. So I thought I'd stump it out myself with the beauty that is Arel. First, the models: class CardSet < ActiveRecord::Base has_and_belongs_to_many :cards, :uniq => true end class Card < ActiveRecord::Base has_and_belongs_to_many :card_sets, :uniq => true has

问题 I have several complex queries (using subqueries, etc...) and want to glue them together with OR or AND statement. For example: where1=table.where(...) where2=table.where(...) I would like something like where3=where1.or where2 Next example doesn't work for me: users.where(users[:name].eq('bob').or(users[:age].lt(25))) because of I have several where(..) queries and I want to concatenate them . In other words I have 3 methods: first return first where, second-second, third - OR concatenation.

问题 I want to restructure the query below using Squeel. I'd like to do this so that I can chain the operators in it and re-use the logic in the different parts of the query. User.find_by_sql("SELECT users.*, users.computed_metric, users.age_in_seconds, ( users.computed_metric / age_in_seconds) as compound_computed_metric from ( select users.*, (users.id *2 ) as computed_metric, (extract(epoch from now()) - extract(epoch from users.created_at) ) as age_in_seconds from users ) as users") The query

问题 I want to restructure the query below using Squeel. I'd like to do this so that I can chain the operators in it and re-use the logic in the different parts of the query. User.find_by_sql("SELECT users.*, users.computed_metric, users.age_in_seconds, ( users.computed_metric / age_in_seconds) as compound_computed_metric from ( select users.*, (users.id *2 ) as computed_metric, (extract(epoch from now()) - extract(epoch from users.created_at) ) as age_in_seconds from users ) as users") The query