I am trying to find all items that are completed inside a list. I tried doing a query inside the Todoitem model, but it is showing [#<Todoitem id: nil>]
What am I doing wrong?
The query I thought goes:
Todoitem.find_by_sql("SELECT count(*) AS count_all FROM todoitems ti INNER JOIN todolists tl WHERE (ti.completed = 'true' AND ti.todolist_id = tl.id)")
my models are like this:
class Todolist < ApplicationRecord
belongs_to :user, required: false
has_many :todoitems, dependent: :destroy
end
class Todoitem < ApplicationRecord
belongs_to :todolist
end
To find all items that are in a todolist and is completed, your query will work. (I am assuming you are storing the boolean value for completed as a string since you used a string in your original query)
However, since you are only selectingcount(*) AS count_all, you will have to look at count_all from the first element in your array like this:
Todoitem.find_by_sql("SELECT count(*) AS count_all FROM todo....").first.count_all
This will return a number of completed todoitems in all todolists in total.
The more active record way of doing this would be like this:
Todolist.joins(:todoitems).where(todoitems:{completed:'true' }).count
To get the number of lists that has at least one completed todoitem, you can use:
Todolist.joins(:todoitems).group(:id).where(todoitems:{completed:'true' }).length
To find how many items that are completed in each list you can use:
Todolist.joins(:todoitems).group(:id).where(todoitems:{completed:'true' }).count
This will return a hash with the id of the list as a key, and the number of completed items as values.
To get the number of completed items in a speciffic task you can use:
Todolist.joins(:todoitems).where(id: id, todoitems:{completed:'true' }).count
You can follow this way.
Rails 5 - Postgresql
In this query, it will show only todolist that has todoitems.
Todolist.select('todolists.id, todolists.title, count(todoitems.todolist_id) as total').joins(:todoitems).group("todolists.id")
Another, This will show only todolist that has no todoitems with 0 result.
Todolist.select('todolists.id, todolists.title, count(todoitems.todolist_id) as total').left_joins(:todoitems).group("todolists.id")
I hope this help you.
Related
Say I have 3 models:
ModelA has many ModelB
ModelB has many ModelC
I'm querying ModelA, but in ModelC I have multiple ones of the same type, let's say I have 3 but I only need the most recently one.
I tried to do something like this...
records = ModelA.where(some query).includes ModelB includes ModelC
// convert activerecord collection to array
records = records.to_a
records.each do |record|
record.modelBs.each do |modelB|
filter the modelCs i don't need
modelB.modelCs = filteredModelCs
end
end
return records
but instead of merely returning the array of records, an UPDATE sql query is run and the db records are modified. this is a surprise because i never used the .save method and i thought i had converted the collection from an active record collection to an array
How can I filter deeply nested records without modifying the db records? then i can return the filtered result
Assigning a list of instances to a has_many collection with = will immediately persist the changes to the database.
Instead, I would try to solve this with more specific associations like this:
class A
has_many :bs
has_many(:cs, through: :bs)
has_one :recent_c, -> { order(created_at: :desc).limit(1) }, source: :cs
class B
has_many :cs
With those associations, I would expect the following to work:
as = A.where(some query).includes(:recent_c)
as.each do |a|
a.recent_c # returns the most recent c for this a
end
If I got you right, you want to get a collection of latest Cs, which are connected to Bs, which are connected to certain A-relation? If so, you can do something like that (considering you have tables as, bs and cs):
class A < ApplicationRecord
has_many :bs
end
class B < ApplicationRecord
belongs_to :a
has_many :cs
end
class C < ApplicationRecord
belongs_to :b
scope :recent_for_bs, -> { joins(
<<-sql
INNER JOIN (SELECT b_id, MAX(id) AS max_id FROM cs GROUP BY b_id) recent_cs
ON cs.b_id = recent_cs.b_id AND cs.id = recent_cs.max_id
sql
) }
end
And then you would query Cs like that:
C.recent_for_bs.joins(b: :a).merge(A.where(some_query))
You get recent Cs, inner join them with Bs and As and then get records connected to your A-relation by merging it.
I have something like this:
duplicates = ['a','b','c','d']
if duplicates.length > 4
Photo.includes(:tags).where('tags.name IN (?)',duplicates)
.references(:tags).limit(15).each do |f|
returned_array.push(f.id)
end
end
duplicates is an array of tags that were duplicated with other Photo tags
What I want is to get Photo which includes all tags from duplicates array, but right now I get every Photo that include at least one tag from array.
THANKS FOR ANSWERS:
I try them and somethings starts to work but wasn't too clear for me and take some time to execute.
Today I make it creating arrays, compare them, take duplicates which exist in array more than X times and finally have uniq array of photos ids.
If you want to find photos that have all the given tags you just need to apply a GROUP and use HAVING to set a condition on the group:
class Photo
def self.with_tags(*names)
t = Tag.arel_table
joins(:tags)
.where(tags: { name: names })
.group(:id)
.having(t[:id].count.eq(tags.length)) # COUNT(tags.id) = ?
end
end
This is somewhat like a WHERE clause but it applies to the group. Using .gteq (>=) instead of .eq will give you records that can have all the tags in the list but may have more.
A better way to solve this is to use a better domain model that doesn't allow duplicates in the first place:
class Photo < ApplicationRecord
has_many :taggings
has_many :tags, through: :taggings
end
class Tag < ApplicationRecord
has_many :taggings
has_many :photos, through: :taggings
validates :name,
uniqueness: true,
presenece: true
end
class Tagging < ApplicationRecord
belongs_to :photo
belongs_to :tag
validates :tag_id,
uniqueness: { scope: :photo_id }
end
By adding unique indexes on tags.name and a compound index on taggings.tag_id and taggings.photo_id duplicates cannot be created.
The issue as I see it is that you're only doing one join, which means that you have to specify that tags.name is within the list of duplicates.
You could solve this in two places:
In the database query
In you application code
For your example the query is something like "find all records in the photos table which also have a relation to a specific set of records in the tags table". So we need to join the photos table to the tags table, and also specify that the only tags we join are those within the duplicate list.
We can use a inner join for this
select photos.* from photos
inner join tags as d1 on d1.name = 'a' and d1.photo_id = photos.id
inner join tags as d2 on d2.name = 'b' and d2.photo_id = photos.id
inner join tags as d3 on d3.name = 'c' and d3.photo_id = photos.id
inner join tags as d4 on d4.name = 'd' and d4.photo_id = photos.id
In ActiveRecord it seems we can't specify aliases for joins, but we can chain queries, so we can do something like this:
query = Photo
duplicate.each_with_index do |tag, index|
join_name = "d#{index}"
query = query.joins("inner join tags as #{join_name} on #{join_name}.name = '#{tag}' and #{join_name}.photo_id = photos.id")
end
Ugly, but gets the job done. I'm sure there would be a better way using arel instead - but it demonstrates how to construct a SQL query to find all photos that have a relation to all of the duplicate tags.
The other method is to extent what you have and filter in the application. As you already have the photos that has at least one of the tags, you could just select those which have all the tags.
Photo
.includes(:tags)
.joins(:tags)
.where('tags.name IN (?)',duplicates)
.select do |photo|
(duplicates - photo.tags.map(&:name)).empty?
end
(duplicates - photo.tags.map(&:name)).empty? takes the duplicates array and removes all occurrences of any item that is also in the photo tags. If this returns an empty array then we know that the tags in the photo had all the duplicate tags as well.
This could have performance issues if the duplicates array is large, since it could potentially return all photos from the database.
I want to get the sum of the receipt items that are in a particular budget (same title) and from the current query I'm getting to many record and obvious wrong sum of amounts from the receipt items.
My current attempt is looking like that in ActiveRecord (AR):
ReceiptItem.includes(donation: [:budgets]).joins(:donation, :receipt).where(budgets: {title: "Some title 2015"}).sum(:amount)
and my SQL attempt was looking like that (its also wrong):
-- want to test just the outcome its not actually not summing up the amounts
SELECT "receipt_items"."amount"
FROM
"receipt_items" INNER JOIN "donations" ON "donations"."id" = "receipt_items"."donation_id"
RIGHT JOIN "receipts" ON "receipts"."receipt_id" = "receipt_items"."receipt_id"
LEFT OUTER JOIN "budgets" ON "budgets"."donation_id" = "donations"."id"
WHERE "budgets"."title" = 'Some title 2015';
Why I'm getting double records although I've joined the tables and set also the condition?
Here is the ER modell to understand the problem.
And here's the AR Assoziations:
class Budget < ActiveRecord::Base
belongs_to :donation
class Donation < ActiveRecord::Base
has_many :receipt_items
has_many :budgets
class ReceiptItem < ActiveRecord::Base
belongs_to :donation
Because a budget can be linked to a reciept item multiple times, via different donations, it's appearing in the big join table multiple times, and thus being counted several times.
Let's try to think this through a step at a time. If you wanted to do it without worrying about eager loading, you would do:
Budget.where(title: "some title").all.collect(&:donation).collect(&:receipt_items).flatten.uniq.collect(&:amount).sum
is that right?
If so, you can tailor the eager loading to fit this chain of method calls:
Budget.where(title: "some title", include: {:donation => [:receipt_items]}).all.collect(&:donation).collect(&:receipt_items).uniq.collect(&:amount).sum
try that?
I have two classes
class Patient < ActiveRecord::Base
belongs_to :camp
has_many :vaccinations
end
class Vaccination < ActiveRecord::Base
belongs_to :patient
end
Each vaccination has members called vaccine_id. A 'complete' vaccination consists of a set of (say) 6 different vaccines, with :names = {A,B,C,D,E,F}.
Patients receive many vaccinations, and I want a report of all the patients who received 'complete' vaccinations. Is there a SQL or ActiveRecord query I can use to get this list of patients?
Perhaps something like:
# in patient.rb
scope :with_completed_vaccinations, ->(number) {
joins(:vaccinations).group('patients.id').
having('COUNT(vaccinations.name) >= ?', number)
}
With this scope you are able to write queries like:
Patient.with_completed_vaccinations(6)
This is an easy way to get all patients who have received complete at least one complete vaccination:
Patient.select { |pat| pat.vaccinations.any? { |vac| vac.complete? } }
And for patients where all vaccinations are complete, just switch the .any? with a .all?
And you could wrap this in a scope, for example by putting this method in your patient.rb
def self.with_complete_vaccinations
select { |pat| pat.vaccinations.any? { |vac| vac.complete? } }
end
This all assumes you have a complete? method defined for your vaccination model.
I've got tables items and cards where a card belongs to a user and a item may or may not have any cards for a given user.
The basic associations are set up as follows:
Class User
has_many :cards
Class Item
has_many :cards
Class Card
belongs_to :user
has_and_belongs_to_many :items
I've also created a join table, items_cards with the columns item_id and card_id. I'd like to make a query that tells me if there's a card for a given user/item. In pure SQL I can accomplish this pretty easily:
SELECT count(id)
FROM cards
JOIN items_cards
ON items_cards.card_id = cards.id
WHERE cards.user_id = ?
AND items_cards.item_id = ?
I'm looking for some guidance as to how I'd go about doing this via ActiveRecord. Thanks!
Assuming you have an Item in #item and a User in #user, this will return 'true' if a card exists for that user and that item:
Card.joins(:items).where('cards.user_id = :user_id and items.id = :item_id', :user_id => #user, :item_id => #item).exists?
Here's what's going on:
Card. - You're making a query about the Card model.
joins(:items) - Rails knows how to put together joins for the association types it supports (usually - at least). You're telling it to do whatever joins are required to allow you to query the associated items as well. This will, in this case, result in JOIN items_cards ON items_cards.card_id = cards.id JOIN items ON items_cards.item_id = items.id.
where('cards.user_id = :user_id and items.id = :item_id', :user_id => #user, :item_id => #item) - Your conditional, pretty much the same as in pure SQL. Rails will interpolate the values you specify with a colon (:user_id) using the values in the hash (:user_id => #user). If you give an ActiveRecord object as the value, Rails will automatically use the id of that object. Here, you're saying you only want results where the card belongs to the user you specify, and there is a row for the item you want.
.exists? - Loading ActiveRecord objects is inefficient, so if you only want to know if something exists, Rails can save some time and use a count based query (much like your SQL version). There's also a .count, which you could use instead if you wanted to have the query return the number of results, rather than true or false.