Related
So i'm currently using the following command to join and query my tables - looking for an OrderItem amongst my Orders where the orderable_id = applicable_product_item_id the total_price = 0 and the buyer_id = current_user
Order.joins(:items)
.where(order_items: {id: OrderItem.where(orderable_id: applicable_product_item_id)})
.where(total_price: 0)
.where(buyer_id: current_user)
This all works fine, but now i want to query further and i want to know if the order that it has found has a created_at date > searchable_created_by_date
i've tried using another .where in the query as well as selecting the .first in the array and further querying that i.e. query = above_query.first
then
query.where("created_at > ?", searchable_created_by_date)
but i get
Undefined method where for #<Order:0x007fbc8d8edf90>
furman87's comment sounds right to me:
You'll have to specify the table in your where clause -- .where("orders.created_at > ?", searchable_created_by_date)
You might also try:
Order.
where(total_price: 0).
where(buyer_id: current_user).
where("created_at > ?", searchable_created_by_date).
joins(:order_items).
where(order_items: {id: OrderItem.where(orderable_id: applicable_product_item_id)})
I think putting the created_at statement before the joins statement will disambiguate the query - but I'm not 100% sure.
Also, I would have thought that you would have done joins(:order_items). But, I suppose that depends on how you have your associations set up. If joins(:items) works for you, then more power to you! (And ignore the comment.)
I have a Company model that has_many Statement.
class Company < ActiveRecord::Base
has_many :statements
end
I want to get statements that have most latest date field grouped by fiscal_year_end field.
I implemented the function like this:
c = Company.first
c.statements.to_a.group_by{|s| s.fiscal_year_end }.map{|k,v| v.max_by(&:date) }
It works ok, but if possible I want to use ActiveRecord query(SQL), so that I don't need to load unnecessary instance to memory.
How can I write it by using SQL?
select t.username, t.date, t.value
from MyTable t
inner join (
select username, max(date) as MaxDate
from MyTable
group by username
) tm on t.username = tm.username and t.date = tm.MaxDate
For these kinds of things, I find it helpful to get the raw SQL working first, and then translate it into ActiveRecord afterwards. It sounds like a textbook case of GROUP BY:
SELECT fiscal_year_end, MAX(date) AS max_date
FROM statements
WHERE company_id = 1
GROUP BY fiscal_year_end
Now you can express that in ActiveRecord like so:
c = Company.first
c.statements.
group(:fiscal_year_end).
order(nil). # might not be necessary, depending on your association and Rails version
select("fiscal_year_end, MAX(date) AS max_date")
The reason for order(nil) is to prevent ActiveRecord from adding ORDER BY id to the query. Rails 4+ does this automatically. Since you aren't grouping by id, it will cause the error you're seeing. You could also order(:fiscal_year_end) if that is what you want.
That will give you a bunch of Statement objects. They will be read-only, and every attribute will be nil except for fiscal_year_end and the magically-present new field max_date. These instances don't represent specific statements, but statement "groups" from your query. So you can do something like this:
- #statements_by_fiscal_year_end.each do |s|
%tr
%td= s.fiscal_year_end
%td= s.max_date
Note there is no n+1 query problem here, because you fetched everything you need in one query.
If you decide that you need more than just the max date, e.g. you want the whole statement with the latest date, then you should look at your options for the greatest n per group problem. For raw SQL I like LATERAL JOIN, but the easiest approach to use with ActiveRecord is DISTINCT ON.
Oh one more tip: For debugging weird errors, I find it helpful to confirm what SQL ActiveRecord is trying to use. You can use to_sql to get that:
c = Company.first
puts c.statements.
group(:fiscal_year_end).
select("fiscal_year_end, MAX(date) AS max_date").
to_sql
In that example, I'm leaving off order(nil) so you can see that ActiveRecord is adding an ORDER BY clause you don't want.
for example you want to get all statements by start of the months you should use this
#companey = Company.first
#statements = #companey.statements.find(:all, :order => 'due_at, id', :limit => 50)
then group them as you want
#monthly_statements = #statements.group_by { |statement| t.due_at.beginning_of_month }
Building upon Bharat's answer you can do this type of query in Rails using find_by_sql in this way:
Statement.find_by_sql ["Select t.* from statements t INNER JOIN (
SELECT fiscal_year_end, max(date) as MaxDate GROUP BY fiscal_year_end
) tm on t.fiscal_year_end = tm.fiscal_year_end AND
t.created_at = tm.MaxDate WHERE t.company_id = ?", company.id]
Note the last where part to make sure the statements belong to a specific company instance, and that this is called from the class. I haven't tested this with the array form, but I believe you can turn this into a scope and use it like this:
# In Statement model
scope :latest_from_fiscal_year, lambda |enterprise_id| {
find_by_sql[..., enterprise_id] # Query above
}
# Wherever you need these statements for a particular company
company = Company.find(params[:id])
latest_statements = Statement.latest_from_fiscal_year(company.id)
Note that if you somehow need all the latest statements for all companies then this most likely leave you with a N+1 queries problem. But that is a beast for another day.
Note: If anyone else has a way to have this query work on the association without using the last where part (company.statements.latest_from_year and such) let me know and I'll edit this, in my case in rails 3 it just pulled em from the whole table without filtering.
I'm hoping there is a easy solution that doesn't involve find_by_sql, if not then I guess that will have to work.
I found this article which references this:
Topic.find(:all, :conditions => { :forum_id => #forums.map(&:id) })
which is the same as
SELECT * FROM topics WHERE forum_id IN (<#forum ids>)
I am wondering if there is a way to do NOT IN with that, like:
SELECT * FROM topics WHERE forum_id NOT IN (<#forum ids>)
Rails 4+:
Article.where.not(title: ['Rails 3', 'Rails 5'])
Rails 3:
Topic.where('id NOT IN (?)', Array.wrap(actions))
Where actions is an array with: [1,2,3,4,5]
FYI, In Rails 4, you can use not syntax:
Article.where.not(title: ['Rails 3', 'Rails 5'])
Using Arel:
topics=Topic.arel_table
Topic.where(topics[:forum_id].not_in(#forum_ids))
or, if preferred:
topics=Topic.arel_table
Topic.where(topics[:forum_id].in(#forum_ids).not)
and since rails 4 on:
topics=Topic.arel_table
Topic.where.not(topics[:forum_id].in(#forum_ids))
Please notice that eventually you do not want the forum_ids to be the ids list, but rather a subquery, if so then you should do something like this before getting the topics:
#forum_ids = Forum.where(/*whatever conditions are desirable*/).select(:id)
in this way you get everything in a single query: something like:
select * from topic
where forum_id in (select id
from forum
where /*whatever conditions are desirable*/)
Also notice that eventually you do not want to do this, but rather a join - what might be more efficient.
You can try something like:
Topic.find(:all, :conditions => ['forum_id not in (?)', #forums.map(&:id)])
You might need to do #forums.map(&:id).join(','). I can't remember if Rails will the argument into a CSV list if it is enumerable.
You could also do this:
# in topic.rb
named_scope :not_in_forums, lambda { |forums| { :conditions => ['forum_id not in (?)', forums.select(&:id).join(',')] }
# in your controller
Topic.not_in_forums(#forums)
To expand on #Trung Lê answer, in Rails 4 you can do the following:
Topic.where.not(forum_id:#forums.map(&:id))
And you could take it a step further.
If you need to first filter for only published Topics and then filter out the ids you don't want, you could do this:
Topic.where(published:true).where.not(forum_id:#forums.map(&:id))
Rails 4 makes it so much easier!
The accepted solution fails if #forums is empty. To workaround this I had to do
Topic.find(:all, :conditions => ['forum_id not in (?)', (#forums.empty? ? '' : #forums.map(&:id))])
Or, if using Rails 3+:
Topic.where( 'forum_id not in (?)', (#forums.empty? ? '' : #forums.map(&:id)) ).all
Most of the answers above should suffice you but if you are doing a lot more of such predicate and complex combinations check out Squeel. You will be able to doing something like:
Topic.where{{forum_id.not_in => #forums.map(&:id)}}
Topic.where{forum_id.not_in #forums.map(&:id)}
Topic.where{forum_id << #forums.map(&:id)}
You may want to have a look at the meta_where plugin by Ernie Miller. Your SQL statement:
SELECT * FROM topics WHERE forum_id NOT IN (<#forum ids>)
...could be expressed like this:
Topic.where(:forum_id.nin => #forum_ids)
Ryan Bates of Railscasts created a nice screencast explaining MetaWhere.
Not sure if this is what you're looking for but to my eyes it certainly looks better than an embedded SQL query.
The original post specifically mentions using numeric IDs, but I came here looking for the syntax for doing a NOT IN with an array of strings.
ActiveRecord will handle that nicely for you too:
Thing.where(['state NOT IN (?)', %w{state1 state2}])
Can these forum ids be worked out in a pragmatic way? e.g. can you find these forums somehow - if that is the case you should do something like
Topic.all(:joins => "left join forums on (forums.id = topics.forum_id and some_condition)", :conditions => "forums.id is null")
Which would be more efficient than doing an SQL not in
This way optimizes for readability, but it's not as efficient in terms of database queries:
# Retrieve all topics, then use array subtraction to
# find the ones not in our list
Topic.all - #forums.map(&:id)
You can use sql in your conditions:
Topic.find(:all, :conditions => [ "forum_id NOT IN (?)", #forums.map(&:id)])
Piggybacking off of jonnii:
Topic.find(:all, :conditions => ['forum_id not in (?)', #forums.pluck(:id)])
using pluck rather than mapping over the elements
found via railsconf 2012 10 things you did not know rails could do
When you query a blank array add "<< 0" to the array in the where block so it doesn't return "NULL" and break the query.
Topic.where('id not in (?)',actions << 0)
If actions could be an empty or blank array.
Here is a more complex "not in" query, using a subquery in rails 4 using squeel. Of course very slow compared to the equivalent sql, but hey, it works.
scope :translations_not_in_english, ->(calmapp_version_id, language_iso_code){
join_to_cavs_tls_arr(calmapp_version_id).
joins_to_tl_arr.
where{ tl1.iso_code == 'en' }.
where{ cavtl1.calmapp_version_id == my{calmapp_version_id}}.
where{ dot_key_code << (Translation.
join_to_cavs_tls_arr(calmapp_version_id).
joins_to_tl_arr.
where{ tl1.iso_code == my{language_iso_code} }.
select{ "dot_key_code" }.all)}
}
The first 2 methods in the scope are other scopes which declare the aliases cavtl1 and tl1. << is the not in operator in squeel.
Hope this helps someone.
If someone want to use two or more conditions, you can do that:
your_array = [1,2,3,4]
your_string = "SOMETHING"
YourModel.where('variable1 NOT IN (?) AND variable2=(?)',Array.wrap(your_array),your_string)
Basically, I have an app with a tagging system and when someone searches for tag 'badger', I want it to return records tagged "badger", "Badger" and "Badgers".
With a single tag I can do this to get the records:
#notes = Tag.find_by_name(params[:tag_name]).notes.order("created_at DESC")
and it works fine. However if I get multiple tags (this is just for upper and lower case - I haven't figured out the 's' bit either yet):
Tag.find(:all, :conditions => [ "lower(name) = ?", 'badger'])
I can't use .notes.order("created_at DESC") because there are multiple results.
So, the question is.... 1) Am I going about this the right way? 2) If so, how do I get all my records back in order?
Any help much appreciated!
One implementation would be to do:
#notes = []
Tag.find(:all, :conditions => [ "lower(name) = ?", 'badger']).each do |tag|
#notes << tag.notes
end
#notes.sort_by {|note| note.created_at}
However you should be aware that this is what is known as an N + 1 query, in that it makes one query in the outer section, and then one query per result. This can be optimized by changing the first query to be:
Tag.find(:all, :conditions => [ "lower(name) = ?", 'badger'], :includes => :notes).each do |tag|
If you are using Rails 3 or above, it can be re-written slightly:
Tag.where("lower(name) = ?", "badger").includes(:notes) do |tag|
Edited
First, get an array of all possible tag names, plural, singular, lower, and upper
tag_name = params[:tag_name].to_s.downcase
possible_tag_names = [tag_name, tag_name.pluralize, tag_name.singularize].uniq
# It's probably faster to search for both lower and capitalized tags than to use the db's `lower` function
possible_tag_names += possible_tag_names.map(&:capitalize)
Are you using a tagging library? I know that some provide a method for querying multiple tags. If you aren't using one of those, you'll need to do some manual SQL joins in your query (assuming you're using a relational db like MySQL, Postgres or SQLite). I'd be happy to assist with that, but I don't know your schema.
I'm hoping there is a easy solution that doesn't involve find_by_sql, if not then I guess that will have to work.
I found this article which references this:
Topic.find(:all, :conditions => { :forum_id => #forums.map(&:id) })
which is the same as
SELECT * FROM topics WHERE forum_id IN (<#forum ids>)
I am wondering if there is a way to do NOT IN with that, like:
SELECT * FROM topics WHERE forum_id NOT IN (<#forum ids>)
Rails 4+:
Article.where.not(title: ['Rails 3', 'Rails 5'])
Rails 3:
Topic.where('id NOT IN (?)', Array.wrap(actions))
Where actions is an array with: [1,2,3,4,5]
FYI, In Rails 4, you can use not syntax:
Article.where.not(title: ['Rails 3', 'Rails 5'])
Using Arel:
topics=Topic.arel_table
Topic.where(topics[:forum_id].not_in(#forum_ids))
or, if preferred:
topics=Topic.arel_table
Topic.where(topics[:forum_id].in(#forum_ids).not)
and since rails 4 on:
topics=Topic.arel_table
Topic.where.not(topics[:forum_id].in(#forum_ids))
Please notice that eventually you do not want the forum_ids to be the ids list, but rather a subquery, if so then you should do something like this before getting the topics:
#forum_ids = Forum.where(/*whatever conditions are desirable*/).select(:id)
in this way you get everything in a single query: something like:
select * from topic
where forum_id in (select id
from forum
where /*whatever conditions are desirable*/)
Also notice that eventually you do not want to do this, but rather a join - what might be more efficient.
You can try something like:
Topic.find(:all, :conditions => ['forum_id not in (?)', #forums.map(&:id)])
You might need to do #forums.map(&:id).join(','). I can't remember if Rails will the argument into a CSV list if it is enumerable.
You could also do this:
# in topic.rb
named_scope :not_in_forums, lambda { |forums| { :conditions => ['forum_id not in (?)', forums.select(&:id).join(',')] }
# in your controller
Topic.not_in_forums(#forums)
To expand on #Trung Lê answer, in Rails 4 you can do the following:
Topic.where.not(forum_id:#forums.map(&:id))
And you could take it a step further.
If you need to first filter for only published Topics and then filter out the ids you don't want, you could do this:
Topic.where(published:true).where.not(forum_id:#forums.map(&:id))
Rails 4 makes it so much easier!
The accepted solution fails if #forums is empty. To workaround this I had to do
Topic.find(:all, :conditions => ['forum_id not in (?)', (#forums.empty? ? '' : #forums.map(&:id))])
Or, if using Rails 3+:
Topic.where( 'forum_id not in (?)', (#forums.empty? ? '' : #forums.map(&:id)) ).all
Most of the answers above should suffice you but if you are doing a lot more of such predicate and complex combinations check out Squeel. You will be able to doing something like:
Topic.where{{forum_id.not_in => #forums.map(&:id)}}
Topic.where{forum_id.not_in #forums.map(&:id)}
Topic.where{forum_id << #forums.map(&:id)}
You may want to have a look at the meta_where plugin by Ernie Miller. Your SQL statement:
SELECT * FROM topics WHERE forum_id NOT IN (<#forum ids>)
...could be expressed like this:
Topic.where(:forum_id.nin => #forum_ids)
Ryan Bates of Railscasts created a nice screencast explaining MetaWhere.
Not sure if this is what you're looking for but to my eyes it certainly looks better than an embedded SQL query.
The original post specifically mentions using numeric IDs, but I came here looking for the syntax for doing a NOT IN with an array of strings.
ActiveRecord will handle that nicely for you too:
Thing.where(['state NOT IN (?)', %w{state1 state2}])
Can these forum ids be worked out in a pragmatic way? e.g. can you find these forums somehow - if that is the case you should do something like
Topic.all(:joins => "left join forums on (forums.id = topics.forum_id and some_condition)", :conditions => "forums.id is null")
Which would be more efficient than doing an SQL not in
This way optimizes for readability, but it's not as efficient in terms of database queries:
# Retrieve all topics, then use array subtraction to
# find the ones not in our list
Topic.all - #forums.map(&:id)
You can use sql in your conditions:
Topic.find(:all, :conditions => [ "forum_id NOT IN (?)", #forums.map(&:id)])
Piggybacking off of jonnii:
Topic.find(:all, :conditions => ['forum_id not in (?)', #forums.pluck(:id)])
using pluck rather than mapping over the elements
found via railsconf 2012 10 things you did not know rails could do
When you query a blank array add "<< 0" to the array in the where block so it doesn't return "NULL" and break the query.
Topic.where('id not in (?)',actions << 0)
If actions could be an empty or blank array.
Here is a more complex "not in" query, using a subquery in rails 4 using squeel. Of course very slow compared to the equivalent sql, but hey, it works.
scope :translations_not_in_english, ->(calmapp_version_id, language_iso_code){
join_to_cavs_tls_arr(calmapp_version_id).
joins_to_tl_arr.
where{ tl1.iso_code == 'en' }.
where{ cavtl1.calmapp_version_id == my{calmapp_version_id}}.
where{ dot_key_code << (Translation.
join_to_cavs_tls_arr(calmapp_version_id).
joins_to_tl_arr.
where{ tl1.iso_code == my{language_iso_code} }.
select{ "dot_key_code" }.all)}
}
The first 2 methods in the scope are other scopes which declare the aliases cavtl1 and tl1. << is the not in operator in squeel.
Hope this helps someone.
If someone want to use two or more conditions, you can do that:
your_array = [1,2,3,4]
your_string = "SOMETHING"
YourModel.where('variable1 NOT IN (?) AND variable2=(?)',Array.wrap(your_array),your_string)