In my rails application, at some point, I query my model simply. I want to query customers order information like how many orders were given by this customer within three months.
Just now, I query the model in that way:
#customer = Customer.all
customer.rb
class Customer < ApplicationRecord
audited
has_many :orders
end
And customer may have orders.
order.rb
class Order < ApplicationRecord
audited
belongs_to :customer
end
What I would like to do is to query customers model and to inject aggregate function result to every customer records.
EDİT
I tried to simulate every solution but couln't achieve.
I have the following query in mysql.
How do I need to code in ruby with activerecord to create that query ?
SELECT
(SELECT
COUNT(*)
FROM
orders o
WHERE
o.customer_id = c.id
AND startTime BETWEEN '2017.12.04' AND '2018.01.04') AS count_last_month,
(SELECT
COUNT(*)
FROM
orders o
WHERE
o.customer_id = c.id
AND startTime BETWEEN '2017.10.04' AND '2018.01.04') AS count_last_three_month,
c.*
FROM
customers c;
How can I achieve that?
Thanks.
Customer.
joins(:orders).
group('customers.id').
where('orders.created_at > DATE_SUB(NOW(), INTERVAL 3 MONTH)')
select('sum(orders.id), customers.*')
As my understanding of you question. I have this solution for you question. Please have a look and try it once. In below query, 'includes' used to solve N+1 problem.
Customer.includes(:orders).where('created_at BETWEEN ? AND ?', Time.now.beginning_of_day, Time.now.beginning_of_day-3.months).group_by{|c|c.orders.count}
If you are looking for particular customer's order count then you can try this one.
#customer.orders.where('created_at BETWEEN ? AND ?', Time.now.beginning_of_day, Time.now.beginning_of_day-3.months).group_by{|c|c.orders.count}
Related
I've been digging around for this for awhile... I can't find a graceful solution. I have loans and loans has_many :decisions. decisions has an attribute that I care about, called risk_rating.
I'd like to sort loans based on the most recent decision (based on created_at, per usual), but by the risk_rating.
Loan.includes(:decisions).references(:decisions).order('decisions.risk_rating DESC') doesn't work...
I want loans... sorted by their most recent decision's risk_rating. This seems like it should be easier than it is.
I'm currently doing this outside of the database like this, but it's chewing up time and memory:
Loan.all.sort do |x,y|
x.decisions.last.try(:risk_rating).to_f <=> y.decisions.last.try(:risk_rating).to_f
end
I'd like to show the performance I'm getting with the proposed answer, along with an inaccuracy...
Benchmark.bm do |x|
x.report{ Loan.joins('LEFT JOIN decisions ON decisions.loan_id = loans.id').group('loans.id').order('MAX(decisions.risk_rating) DESC').limit(10).map{|l| l.decisions.last.try(:risk_rating)} }
end
user system total real
0.020000 0.000000 0.020000 ( 20.573096)
=> [0.936775, 0.934465, 0.932088, 0.922352, 0.921882, 0.794724, 0.919432, 0.918385, 0.916952, 0.914938]
The order isn't right. That 0.794724 is out of place.
To that extent... I'm only seeing one attribute in the proposed answer. I don't see the connection =/
Alright, it looks like I'm working late tonight because I couldn't help but jump in:
class Loan < ApplicationRecord
has_many :decisions
has_one :latest_decision, -> { merge(Decision.latest) }, class_name: 'Decision'
end
class Decision < ApplicationRecord
belongs_to :loan
def latest
t1 = arel_table
t2 = arel_table.alias('t2')
# Self join based on `loan_id` prefer latest `created_at`
join_on = t1[:loan_id].eq(t2[:loan_id]).and(
t1[:created_at].lt(t2[:created_at]))
where(t2[:loan_id].eq(nil)).joins(
t1.create_join(t2, t1.create_on(join_condition), Arel::Nodes::OuterJoin)
)
end
end
Loan.includes(:latest_decision)
This doesn't sort, just provides the latest decision for each loan. Throwing an order that references access_codes messes things up because of the table aliasing. I don't have the time to work that kink out now, but I bet you can figure it out if you check out some of the great resources on Arel and how to use it with ActiveRecord. I really enjoy this one.
At first let's write sql-query which will select necessary data. SO contains a question which may helps here: Select most recent row with GROUP BY in MySQL. My best version:
SELECT loans.*
FROM loans
LEFT JOIN (
SELECT loan_id, MAX(id) as id
FROM decisions
GROUP BY loan_id) d ON d.loan_id = loans.id
LEFT JOIN decisions ON decisions.id = d.id
ORDER BY decisions.risk_rating DESC
This code suppose MAX(id) gives id of the recent row in group.
You may do the same query by this Rails code:
sub_query =
Decision.select('loan_id, MAX(id) as id').
group(:loan_id).to_sql
Loan.
joins("LEFT JOIN (#{sub_query}) d ON d.loan_id = loans.id").
joins("LEFT JOIN decisions ON decisions.id = d.id").
order("decisions.risk_rating DESC")
Unfortunately, I don't have MySQL at hand and I can't try this code. Hope it will work.
here are my models:
class Article
has_many :votes
end
class Vote
belongs_to :article
belongs_to :user
end
Now I am trying to order the articles, by the count of votes in the past 24 hours. Any suggestions for how to do this?
I have tried this:
Article.left_joins(:votes).group("articles.id").order("count(votes.id) DESC")
However, this is ordering by all the votes, not the votes in last 24h. Any suggestions?
One more thing is, I still need to get the articles with no votes. So I am not sure how to use the where clause here...
You need to add the date when the vote was created for an article prior to the count of votes in your order.
Try this:
Article.left_joins(:votes)
.group("articles.id")
.order("DATE(votes.created_at) DESC, count(votes.id) DESC")
Then if you only want to get the articles that has been upvoted for the past 24hr, you can chain this to your query:
.where("votes.created_at >= ?", 1.day.ago)
Finally I got it work. It turns out left_joins is not necessary. My current solution is using select clause in the order() function:
Article.order("(select count(*) from votes where votes.article_id = articles.id and votes.created_at >= NOW() - '1 day'::INTERVAL ) desc")
Maybe not elegant, but works well.
I came across about the problem excluding data, if the attribute x of one of the associated data has the value 'a'.
Example:
class Order < ActiveRecord::Base
has_many :items
end
class Item < ActiveRecord::Base
belongs_to :order
validate_presence_of :status
end
The query should return all Orders that don't have an Item with status = 'paid' (status != 'paid').
Because of the 1:n association an Order can have many Items. And one of the Itmes can have the status = 'paid'. These Orders must be excluded from the result of my query even if the order has other items with status different from 'paid'.
How would I solve this problem:
paid_items = Items.where(status: 'paid').pluck(:order_id)
orders_wo_paid = Order.where('id NOT IN (?)', paid_items)
Is there an ActiveRecord solution, that solves this problem in one query.
Or are there other ways to solve this question?
I 'm not looking for ruby solution such as:
Order.select do |order|
!order.items.pluck(:status).include?('paid')
end
thx for ideas and inspirations.
You can do:
Order.where('orders.id NOT IN (?)', Item.where(status: 'paid').select(:order_id))
If you're using Rails 4.x then:
Order.where.not(id: Item.where(status: 'paid').select(:order_id))
The query you are interested in is the following, but creating with activerecord will be hard/no very readable:
SELECT
orders.*
FROM
orders
LEFT JOIN
order_items ON orders.id = order_items.order_id
GROUP BY
order_items.order_id
HAVING
COUNT(DISTINCT order_items.id) = COUNT(DISTINCT order_items.status <> 'paid')
Sorry for the sql indentation, I have no idea which are the conventions for it.
A way (not the best one at all) to it with rails (unfortunately writing sql for the most important parts) would be the following:
Order.group(:order_id).joins("LEFT JOIN order_items ON orders.id = order_items.order_id")
.having("COUNT(DISTINCT order_items.id) = COUNT(DISTINCT order_items.status <> 'paid')")
Of course you can play with AREL to get rid of the hard coded sql, but in my opinion it will not be easier to read.
You can have an example of creating lefts joins in this gist: https://gist.github.com/mildmojo/3724189
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.
Try next one:
Question.joins(:votes).select("questions.id, *other question coulmns*, count(votes.id) as vote_count").order("vote_count DESC").group("questions.id")
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 = questions.id")
Solution is DB agnostic. Make sure you add an index on the question_id column in the votes table( you should add the index even if you don't use this solution).
The problem I'm having is like this: The model to sort is SchoolClass which has_many Students which in turn has_many Projects and each project has an end_date. I need to sort the SchoolClasses four ways: First by the earliest project end_date sort ascending and descending, and second by the latest project end_date sort ascending and descending. Does this make sense?
class SchoolClass < ActiveRecord::Base
has_many :students
end
class Student < ActiveRecord::Base
has_many :projects
belongs_to :school_class
end
class Project < ActiveRecord::Base
belongs_to :student
end
The only way I can think of doing it is very brute force and involves having a methods in the SchoolClass model that return the earliest and latest project dates for that instance like so:
students.collect(&:projects).flatten.select(&:end_date).sort.last
to find the latest project end_date for that class and then fetching out all the classes of the database and sorting them by that method. Surely this is just awful though, right? I would really like to find the rails way to get this ordering (with scopes maybe?). I thought something like SchoolClasses.joins(:students).joins(:projects).order('projects.end_date ASC') might work but that will crash rails (and looking at it now the logic is wrong anyway i think).
Any suggestions?
Try this:
scs = SchoolClass.joins({:students => :projects}).
select("school_classes.id,
MIN(projects.end_date) AS earliest_end_date,
MAX(projects.end_date) AS latest_end_date").
group("school_classes.id").
order("earliest_end_date ASC")
The objects in the scs array has following attributes:
id
earliest_end_date
latest_end_date
If you need additional attributes you can do the following
1) Add the additional attributes to the group and select methods
2) Query the full SchoolClass object using the id
3) Rewrite the query to use a nested JOIN
scs = SchoolClass.joins(
"JOIN (
SELECT a.id,
MIN(c.end_date) AS earliest_end_date,
MAX(c.end_date) AS latest_end_date
FROM school_classes a
JOIN students b ON b.class_id = a.id
JOIN projects c ON c.student_id = b.id
GROUP BY a.id
) d ON d.id = school_classes.id
").select("school_classes.*,
d.earliest_end_date AS earliest_end_date,
d.latest_end_date AS latest_end_date").
order("earliest_end_date ASC")