I am getting missing FROM clause error (shown below)
I want to find the entries whose associated reports' city is the same as the users' city, thus only showing relavant entries to users. So, if a user belongs to a city that a report does, the user should be shown the entries from that report.
I tried a few things, one being this scope in the Entry model:
scope :report_in_city, lambda { |user| joins(:report).where("report.city_id = ?", user.city_id) }
And if I call Entry.report_in_city(user)
I get this error:
SELECT "entries".* FROM "entries" INNER JOIN "reports" ON "reports"."id" = "entries"."report_id" WHERE (report.city_id = 1)
ActiveRecord::StatementInvalid: PG::Error: ERROR: missing FROM-clause entry for table "report"
LINE 1: ... ON "reports"."id" = "entries"."report_id" WHERE (report.cit...
^
: SELECT "entries".* FROM "entries" INNER JOIN "reports" ON "reports"."id" = "entries"."report_id" WHERE (report.city_id = 1)
I have a few models set up like this:
class Report
belongs_to user
belongs_to city
has_many entries
class Entry
belongs_to report
class User
has_many reports
belongs_to city
class City
has_many users
has_many reports
I am new to sql and would appreciate any advice on this query!
Since that string condition "report.city_id = ?" goes into the SQL, you have to use the table names. Rails is cute about going back and forth between plural and singular, but SQL only knows the table name reports. You can see that in the generated SQL like ON "reports"."id" = "entries"."report_id". The table name is plural.
Try this:
"reports.city_id = ?"
or the Rails way:
joins(:report).where(:report => { :city_id => user.city_id })
Related
I have a Student model and that model has_many subscriptions. I need to return all students who have subscriptions. this object must contain only the student's name, email, phone and status, in addition to the subscription id and recurrence_code. I thought something more or less like this but I can't succeed in the query:
students = Student.all.includes(:subscriptions)
students.each do |student|
student.select(:id, :name, :email, :phone, :status, subscription: {
methods: [:id, :recurrency_code]}
end
This is a classic inner join scenario
class Student < ApplicationRecord
has_many :subscriptions
end
class Subscription < ApplicationRecord
belongs_to :student
end
I find it helpful to break these problems into steps:
"Only Students where a Subscription record is present" is a standard inner join:
Student.joins(:subscriptions).uniq
"object must contain only the student's name, email, phone and status"
Student.joins(:subscriptions).select(:name, :email, :phone, :status).uniq
"in addition to the subscription id and recurrence_code"
students = Student.joins(:subscriptions)
.select(
'students.name, students.email,'\
'students.phone, students.status, '\
'subscriptions.id as subscription_id,'\
'subscriptions.recurrence_code as subscription_recurrence_code'
)
A few notes:
1. Using select with joins
#vee's SO Answer here points out:
If the column in select is not one of the attributes of the model on which the select is called on then those columns are not displayed. All of these attributes are still contained in the objects within AR::Relation and are accessible as any other public instance attributes.
This means if you load an individual record (e.g. students.first), you will only see the Student attributes by default. But you can still access the Subscription attributes by the as name you set in the query. E.g.:
students.first.subscription_recurrence_code
2. Use .uniq to eliminate duplicates.
Because of the has_many relationship, the query Student.joins(:subscriptions) will return a record for each subscription, which means each student will appear in the result the same number of times as they have subscriptions. Calling .uniq (short for unique) will remove duplicates from the result.
I'm agree with the Chiperific response, but I disagree to use the uniq method because it doesn't call the 'DISTINCT' in the SQL query.
Rails: uniq vs. distinct
For me it's better to use distinct. So the query could be as this:
Student.joins(:subscriptions).distinct.select(
:name, :email, :phone, :status,
'subscriptions.id AS subscription_id',
'subscriptions.recurrence_code'
)
I have user model which has_one association with user_profile
And I want to select name field from user_profile instead of user_profile.*
I have tried,
user = User.first
user.user_profile.select(:name)
But this is not working.any way?
UPDATED:
It seems, that rails handles the other direction and one-to-one connections differently. You have two options:
1) Define the selected attributes in the association, it will always select those
has_one :user_profile, :select => [:name, :id]
2) Define a specific find in your model, where you can add select, like this:
def my_profile
UserProfile.find(self.user_profile_id)
end
....
my_profile.select(:name)
ORIGINAL:
In case of has_many direction, it works:
I've tried your method in my code, like:
= User.find("admin").article.select(:title).to_sql
It returns the correct sql:
SELECT title
FROM "articles"
WHERE "articles"."user_id" = 1364
I'm trying to do some fairly complicated record sorting that I was having a bit of trouble with. I have three models:
class User < ActiveRecord::Base
has_many :registers
has_many :results, :through => :registers
#Find all the Users that exist as registrants for a tournament
scope :with_tournament_entrees, :include => :registers, :conditions => "registers.id IS NOT NULL"
end
Register
class Register < ActiveRecord::Base
belongs_to :user
has_many :results
end
Result
class Result < ActiveRecord::Base
belongs_to :register
end
Now on a Tournament result page I list all users by their total wins (wins is calculated through the results table). First thing first I find all users who have entered a tournament with the query:
User.with_tournament_entrees
With this I can simply loop through the returned users and query each individual record with the following to retrieve each users "Total Wins":
user.results.where("win = true").count()
However I would also like to take this a step further and order all of the users by their "Total Wins", and this is the best I could come up with:
User.with_tournament_entrees.select('SELECT *,
(SELECT count(*)
FROM results
INNER JOIN "registers"
ON "results"."register_id" = "registers"."id"
WHERE "registers"."user_id" = "users.id"
AND (win = true)
) AS total_wins
FROM users ORDER BY total_wins DESC')
I think it's close, but it doesn't actually order by the total_wins in descending order as I instruct it to. I'm using a PostgreSQL database.
Edit:
There's actually three selects taking place, the first occurs on User.with_tournament_entries which just performs a quick filter on the User table. If I ignore that and try
SELECT *, (SELECT count(*) FROM results INNER JOIN "registers" ON "results"."register_id" = "registers"."id" WHERE "registers"."user_id" = "users.id" AND (win = true)) AS total_wins FROM users ORDER BY total_wins DESC;
it fails in both PSQL and the ERB console. I get the error message:
PGError: ERROR: column "users.id" does not exist
I think this happens because the inner-select occurs before the outer-select so it doesn't have access to the user id before hand. Not sure how to give it access to all user ids before than inner select occurs but this isn't an issue when I do User.with_tournament_entires followed by the query.
In your SQL, "users.id" is quoted wrong -- it's telling Postgres to look for a column named, literally, "users.id".
It should be "users"."id", or, just users.id (you only need to quote it if you have a table/column name that conflicts with a postgres keyword, or have punctuation or something else unusual).
I am trying to do a QUERY in my controller to get a list of suppliers with a category ID.
I have my models set up like this.
class Supplier < ActiveRecord::Base
has_and_belongs_to_many :sub_categories
end
class Category < ActiveRecord::Base
has_many :sub_categories
end
class SubCategory < ActiveRecord::Base
belongs_to :category
has_and_belongs_to_many :suppliers
end
A supplier can have Many sub_categories that are under one single category. So i can grab the category of a supplier by doing this.
#supplier.sub_categories.first.category.name
This returns the category that the supplier comes under because they have to have at least 1 sub category which is then linked to a category.
What i am trying to do is by passing a category_id i wish to return all suppliers that come under that category.
I had it written like this but it doesnt seem to be working.
#category = Category.find(params[:category_id])
#suppliers = Supplier.where('sub_category.first.category.id = ?', #category.id)
i get the following sql error
Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.id = 20)' at line 1: SELECT `suppliers`.* FROM `suppliers` WHERE (sub_category.first.category.id = 20)
Well, that's certainly an sql error. The stuff inside the where() call gets translated directly to SQL, and that's not sq;l. :)
You need to join tables together. I'm assuming there's a sub_category_suppliers table that completes the habtm association. (BTW, I much prefer to use has_many :through exclusively)
I think it would be something like this:
Supplier.joins(:sub_category_suppliers => :sub_categories).
where('sub_categories.category_id =?', #category.id).
group('suppliers.id')
As Caley Woods suggested, this should be placed in the Supplier model as a scope:
scope :by_category, lambda { |category_id|
joins(:sub_category_suppliers => :sub_categories).
where('sub_categories.category_id =?', category_id).
group('suppliers.id')
}
and then called as Supplier.by_category(#category.id)
I'm trying join in Rails 3 for the first time, and can't get the most basic thing to work, so must be missing something major. Given
class Member < ActiveRecord::Base
belongs_to :status
...
end
class Status ActiveRecord::Base
has_many :members
...
end
when I try to use a join, testing in the console an example adapted from the Rails Guides
time_range = (Time.now.midnight - 1.day)..Time.now.midnight
Status.joins(:members).where('member.created_at' => time_range)
I get an error message,
ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'member.created_at' in
'where clause': SELECT `statuses`.* FROM `statuses` INNER JOIN `members` ON
`members`.`status_id` = `statuses`.`id` WHERE (`member`.`created_at` BETWEEN
'2011-03-26 23:00:00' AND '2011-03-27 23:00:00')
Both models do have created_at columns and this works: Member.where(:created_at => time_range). I've tried several permutations and used different columns but get the same Unknown column error every time I try the join.
It should be members.created_at :) When you explicitly use the db table name, remember that it's in plural by rails convention.