I like to simplify my approach to the following query. (Using MySQL and Rails 5.0.1)
I have a Prospect with many Results. I want to generate a list of last updated Results on all Prospects with results to use in my controller.
Prospect
has_many :results
Result
has_one :Prospect
This works in my Propects model
def self.last_results
customer_ids=Result.where("results.disposition" => "appointment").where.not("results.event" => nil).distinct.pluck(:prospect_id)
all=[]
customer_ids.each { |c|
last_result= self.includes(:prospect)
.where("results.prospect_id" => c)
.order("results.created_at ASC")
.last
all << last_result
}
return all
end
I think there must be an easier rails way to do this without creating multiple loops with queries.
Related
I am using Ruby v1.8 and Rails v2.3.
I have a two model objects: Cars and Customers,
Model Cars:
class car < ActiveRecord::Base
#car has attribute :town_code
has_many :customers
end
Model Customers:
class customer < ActiveRecord::Base
# customer has attribute :first_name, :last_name
belongs_to :car
end
Now in my controller, I got a string from VIEW, and the received string has the format firstname.lastname#town_code, for example a string like "John.smith#ac01" which can be parsed as first_name="John", last_name="smith" and town_code="ac01"
Now I would like use the Rails's way to query the database to find all the customer objects (match the above conditions) from Customers table which has :
first_name="John",
last_name="smith"
and owned a car(by car_id) with car's town_code="ac01".
what is Rails' syntax to query this?
I know it should be something like (if I wanna count the nr of matched customer):
Customer.count :consitions =>{:first_name => "John", :last_name=>"smith"...}
But, I am not sure how to refer to a customer that has a referenced car with car's town_code= "ac01" ?
------------------ My question --------------------
I want to have two queries:
-one is used to count the number of matching customers,
-the other query returns the customers objects like find_by_ query.
What is the syntax in Ruby on Rails for the two queries?
It should be something similar to
Customer.where(:firstname => "John", :last_name => "Smith").count
If you have many Customers of Car, you can do something like
Car.where(...).customers.where(...)
You should really be firing rails c to test your queries in (I might be slightly off)
You could have something like:
#customers = car.where(:town_code => town_code).customers.where(:first_name => first_name, :last_name => last_name)
And then just count the results:
#customer_count = #customers.count
This assuming you parsed your string into the variables town_code, first_name, and last_name, like you said.
Edit
I don't think Rails v2.3 supports these chains of Active Record queries because I believe it lacks lazy loading from DB. I'm not completely sure. Also, I realize my first suggestion would't work because there could be many cars with the same town_code. I guess you could solve it using the map function like so (not tested):
#customers = car.all(:conditions => {:town_code => town_code}).map{ |c| c.customers.where(:first_name => first_name, :last_name => last_name) }
And then count them like before:
#customer_count = #customers.count
I believe you could do something like this: source
Customer.find(:all, :include => :car, :conditions => "customers.first_name = 'John' AND customers.last_name = 'Smith' AND cars.town_code = 'ac01'")
Counting all customers with a specification can be achieved by this command: source
Customer.count(:all, :include => :car, :conditions => "customers.first_name = 'John' AND customers.last_name = 'Smith' AND cars.town_code = 'ac01'")
By the way, if you are in the position to choose what you work with, I would advise you to go for Rails 3. The chaining methods described by Joseph would make this kind of query a lot easier and it'll save you upgrading issues down the road. (And you tagged the question for Rails 3)
I have a relationship table in a rails application called edit_privileges, in which the User is the "editor" and a number of other classes are "editable". Let's say that two of those classes are Message and Comment.
My EditPrivilege model uses the following code:
belongs_to :editor, :class_name => "User"
belongs_to :editable, :polymorphic => true
And User, of course
has_many :edit_privileges, :foreign_key => "editor_id"
In order to determine if a user has edit privileges for a certain model, I can't do the normal query:
user.edit_privileges.find_by_editable_id(#message.id)
because if the user has edit privileges to edit a comment with the same id as #message, the query will return true with the wrong edit privilege record from the table.
So, I tried doing these options:
user.edit_privileges.find(:all, :conditions => ["editable_id = ? AND editable_type ?", #message.id, #message.class.to_s])
user.edit_privileges.where(:editable_id => #message.id, :editable_type => #message.class.to_s)
which works great at finding the right record, but returns an array instead of an object (an empty array [] if there is no edit privilege). This is especially problematic if I'm trying to create a method to destroy edit privileges, since you can't pass .destroy on an array.
I figure appending .first to the two above solutions returns the first object and nil if the result of the query is an empty has, but is that really the best way to do it? Are there any problems with doing it this way? (like, instead of using dynamic attribute-based finders like find_by_editabe_id_and_editable_type)
Use find(:first, ...) instead of find(:all, ...) to get one record (note it might return nil while find will raise an RecordNotFound exception). So for your example:
user.edit_privileges.find(:first, :conditions => { :editable_id => #message.id, :editable_type => #message.class.to_s })
BTW, if you're on more edge rails version (3.x), Model.where(...).first is the new syntax:
user.edit_privileges.where(:editable_id => #message.id, :editable_type => #message.class.to_s).first
I have several similar models ContactEmail, ContactLetter, etcetera.
Each one belongs_to a Contact
Each contact belongs_to a Company
So, what I did was create a virtual attribute for ContactEmail:
def company_name
contact = Contact.find_by_id(self.contact_id)
return contact.company_name
end
Question: How can I get an easy list of all company_name (without duplicates) if I have a set of ContactEmails objects (from a find(:all) method, for example)?
When I try to do a search on ContactEmail.company_name using the statistics gem, for example, I get an error saying that company_name is not a column for ContactEmail.
Assuming your ContactEmail set is in #contact_emails (untested):
#contact_emails.collect { |contact_email| contact_email.company_name }.uniq
You don't need the virtual attribute for this purpose though. ActiveRecord sets up the relationship automatically based on the foreign key, so you could take the company_name method out of the ContactEmail model and do:
#contact_emails.collect { |contact_email| contact_email.contact.company_name }.uniq
Performance could be a consideration for large sets, so you might need to use a more sophisticated SQL query if that's an issue.
EDIT to answer your 2nd question
If company_name is a column, you can do:
ContactEmail.count(:all, :joins => :contact, :group => 'contact.company_name')
On a virtual attribute I think you'd have to retrieve the whole set and use Ruby (untested):
ContactEmail.find(:all, :joins => :contact, :select => 'contacts.company_name').group_by(&:company_name).inject({}) {|hash,result_set| hash.merge(result_set.first=>result_set.last.count)}
but that's not very kind to the next person assigned to maintain your system -- so you're better off working out the query syntax for the .count version and referring to the column itself.
I just got referred to stackoverflow by a friend here to help with a problem I am having. I am fairly new to ruby on rails and I am working on a collaborative project where we have a script (medal_worker.rb) that is scheduled to run at a fixed intervals to award people various medals based on various participation and success on our website. One of the new medals I am working on rewards people for "milestones". For the purpose of this problem, let's say we want to give them medals when they make 100, 1000, and 10000 comments. I would like to do this by using named_scopes from the User model (user.rb) to give me filtered lists of the users I am looking for.
My question is: How do I find the users who do not have the respective medals for the respective milestone comment level (preferably using the named_scopes from the User model)?
Here is an exerpt from my model_worker.rb file:
def award_comment_milestone(comments)
users = Users.frequent_comment_club_members(comments).not_awarded_medal(Medal.find_by_id(medal.id))
for user in users do
award_medal(medal, nil, user) if #award
end
end
Here is where I am at with the named_scopes in the user model (user.rb):
named_scope :frequent_comment_club_members, lambda { |*args|
{:include => comment_records, :conditions => ['comment_records.comment_type = ? and comment_records.comments >= ?', 'User', (args.first || 0)]}
}
named_scope :not_awarded_medal, lambda { |medal|
{:include => :awards, :conditions => ['awards.medal_id not in (select awards.medal_id from awards where awards.medal_id = ?)", medal.id] }
}
This is not working as I would like, but I don't know if the problem is in the named_scopes or how I am passing arguements or what. Thanks.
Your named_scopes look fine. Except you are starting with a single apostrophe and ending with a double apostrophe in the not_awarded_medal condition statement.
EDIT:
Take it back. Your not_awarded_medal named_scope is off.
Try something like this:
named_scope :not_awarded_medal, lambda { |medal_id|
{ :include => :awards,
:conditions => [
"? not in (select awards.id from awards where awards.user_id = users.id)", medal_id
]
}
}
untested
Now this is assuming that you have the following relationships:
User: has_many :awards
Award: belongs_to :user
If you are using has_many :through then you are going to have to change the SQL to look at the join (users_awards) table.
--
But I do see a couple of things in the award_comment_milestone function.
What is the parameter coming into award_comment_milestone? Is it an array of comments or is it a count of comments? Also where is medal defined?
If comments is an array then you need to pass comments.length into frequent_comment_club_members. If it's the count then I would rename it to comments_count so the next person can understand the logic more quickly.
Some general observations:
not_awarded_medal should just take a medal_id and not the whole object (no need to do multiple queries)
Why are you doing Medal.find_by_id(medal.id)? You already have the medal object.
I have the following model association: a student model and has_many scores.
I need to make a list showing their names and average, min, max scores. So far I am using
student.scores.average(:score) on each student, and I realise that it is doing one sql per student. How can I make the list with one joined sql?
Also how would I use that with Will_Paginate plugin?
Thank you
You want the :group and :select options to Student.find. This should work for you:
students = Student.all(
:select => "
students.*,
AVG(scores.score) as avg_score,
MIN(scores.score) as min_score,
MAX(scores.score) as max_score",
:joins => :scores
:group => 'students.id')
The calculated columns are available just like the real columns though they obviously won't be saved
students.first.avg_score
students.first.min_score
students.first.max_score
For using WillPaginate, just include your :page, :per_page, ... options and call Student.paginate instead of find. If it turns out that the pagination is getting the wrong number of pages because of the :group option, just add this: :total_entries => Student.count to your arguments