Theoretically what I want is this:
:order => "column1 ASC, column2 DESC"
But column1 is actually not a column in my case but an aggregated value:
:order => relations.count
How can I order by two columns when one of those is actually an aggregated value?
Btw: Counter-Cache is not an option (because it is outdated when I need it)
:order => "COUNT(*), column2 DESC"
To order/group/etc by a calculated value, you have to specify it in the corresponding clause, in your case using a (possibly left) join too:
Something.select("somethings.*, COUNT(others.id)").
joins("LEFT JOIN others ON others.something_id = somethings.id").
group("somethings.*").
order("COUNT(others.id), column2 DESC")
Related
I have a model with the fields price, min_price,max_price, discount,in my product table. if I want to execute ascending descending orders, how that will get executed when we apply for an order on multiple fields. for example like below.
#products = Product.order("price asc").order("min_price desc").order("max_price asc").order("updated_at asc") (Query might be wrong but for reference im adding)
will it order as per the order sequence ?
If you append .to_sql to that, it will show the generated SQL so you can investigate yourself.
I tried a similar query:
Book.select(:id).order("id asc").order("pub_date desc").to_sql
=> "SELECT \"books\".\"id\" FROM \"books\" ORDER BY id asc, pub_date desc"
You might instead:
Book.select(:id).order(id: :asc, pub_date: :desc).to_sql
=> "SELECT \"books\".\"id\" FROM \"books\" ORDER BY \"books\".\"id\" ASC, \"books\".\"pub_date\" DESC"
... which you see adds the table name in, so is more reliable when if you are accessing multiple tables
Is it possible to sort the data on a condition?
For example, figuratively, .order( "expiration_date <?", Time.current, :desc )
The ORDER BY keyword is used to sort the result-set by one or more columns.
The ORDER BY keyword sorts the records in ascending order by default. To sort the records in a descending order, you can use the DESC keyword.
you can sort by using something like :-
sorted = #records.sort_by &:created_at
or try where by first getting the resultset and then sorting it:-
#records.where( "expiration_date <?", Time.current).order( :created_at, :desc )
Moreover you can paginate easily;-
#records.paginate(:page => params[:page], :per_page => 15)#.order(" created_at ASC")
I want to sort by two columns, one is a DateTime (updated_at), and the other is a Decimal (Price)
I would like to be able to sort first by updated_at, then, if multiple items occur on the same day, sort by Price.
In Rails 4 you can do something similar to:
Model.order(foo: :asc, bar: :desc)
foo and bar are columns in the db.
Assuming you're using MySQL,
Model.all(:order => 'DATE(updated_at), price')
Note the distinction from the other answers. The updated_at column will be a full timestamp, so if you want to sort based on the day it was updated, you need to use a function to get just the date part from the timestamp. In MySQL, that is DATE().
Thing.find(:all, :order => "updated_at desc, price asc")
will do the trick.
Update:
Thing.all.order("updated_at DESC, price ASC")
is the Rails 3 way to go. (Thanks #cpursley)
Active Record Query Interface lets you specify as many attributes as you want to order your query:
models = Model.order(:date, :hour, price: :desc)
or if you want to get more specific (thanks #zw963 ):
models = Model.order(price: :desc, date: :desc, price: :asc)
Bonus: After the first query, you can chain other queries:
models = models.where('date >= :date', date: Time.current.to_date)
Actually there are many ways to do it using Active Record. One that has not been mentioned above would be (in various formats, all valid):
Model.order(foo: :asc).order(:bar => :desc).order(:etc)
Maybe it's more verbose, but personally I find it easier to manage.
SQL gets produced in one step only:
SELECT "models".* FROM "models" ORDER BY "models"."etc" ASC, "models"."bar" DESC, "models"."foo" ASC
Thusly, for the original question:
Model.order(:updated_at).order(:price)
You need not declare data type, ActiveRecord does this smoothly, and so does your DB Engine
Model.all(:order => 'updated_at, price')
None of these worked for me!
After exactly 2 days of looking top and bottom over the internet, I found a solution!!
lets say you have many columns in the products table including: special_price and msrp. These are the two columns we are trying to sort with.
Okay, First in your Model
add this line:
named_scope :sorted_by_special_price_asc_msrp_asc, { :order => 'special_price asc,msrp asc' }
Second, in the Product Controller, add where you need to perform the search:
#search = Product.sorted_by_special_price_asc_msrp_asc.search(search_params)
If i have two tables Books, CDs with corresponding models.
I want to display to the user a list of books and CDs. I also want to be able to sort this list on common attributes (release date, genre, price, etc.). I also have basic filtering on the common attributes.
The list will be large so I will be using pagination in manage the load.
items = []
items << CD.all(:limit => 20, :page => params[:page], :order => "genre ASC")
items << Book.all(:limit => 20, :page => params[:page], :order => "genre ASC")
re_sort(items,"genre ASC")
Right now I am doing two queries concatenating them and then sorting them. This is very inefficient. Also this breaks down when I use paging and filtering. If I am on page 2 of how do I know what page of each table individual table I am really on? There is no way to determine this information without getting all items from each table.
I have though that if I create a new Class called items that has a one to one relationship with either a Book or CD and do something like
Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "genre ASC")
However this gives back an ambiguous error. So can only be refined as
Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "books.genre ASC")
And does not interleave the books and CDs in a way that I want.
Any suggestions.
The Item model idea will work, but you are going to have to pull out all the common attributes and store them in Item. Then update all you forms to store those specific values in the new table. This way, adding a different media type later would be easier.
Update after comment:
What about a union? Do find_by_sql and hand-craft the SQL. It won't be simple, but your DB scheme isn't simple. So do something like this:
class Item < ActiveModel::Base
attr_reader :title, :genre, :media_type, ...
def self.search(options = {})
# parse options for search criteria, sorting, page, etc.
# will leave that for you :)
sql = <<-SQL
(SELECT id, title, genre, 'cd' AS media_type
FROM cds
WHERE ???
ORDER BY ???
LIMIT ???
) UNION
(SELECT id, title, genre, 'book' AS media_type
FROM books
WHERE ???
ORDER BY ???
LIMIT ???
)
SQL
items = find_by_sql(sql)
end
end
untested
Or something to that effect. Basically build the item rows on the fly (you will need a blank items table). The media_type column is so you know how to create the links when displaying the results.
Or...
Depending on how often the data changes you could, gasp, duplicate the needed data into the items table with a rake task on a schedule.
You say you can't change how books and CDs are stored in the database, but could you add an items view? Do you have any control over the database at all?
CREATE VIEW items
(id, type, title, genre, created_at, updated_at)
AS
SELECT b.id, 'Book', b.title, b.genre, b.created_at, b.updated_at
FROM books b
UNION
SELECT c.id, 'CD', c.title, c.genre, c.created_at, c.updated_at
FROM cds c;
You can paginate on a results array, so leave pagination out of the invidual model queries, and add it to your results array:
re_sort(items,"genre ASC").paginate(:page => params[:page], :per_page => items_per_page)
In my online store, an order is ready to ship if it in the "authorized" state and doesn't already have any associated shipments. Right now I'm doing this:
class Order < ActiveRecord::Base
has_many :shipments, :dependent => :destroy
def self.ready_to_ship
unshipped_orders = Array.new
Order.all(:conditions => 'state = "authorized"', :include => :shipments).each do |o|
unshipped_orders << o if o.shipments.empty?
end
unshipped_orders
end
end
Is there a better way?
In Rails 3 using AREL
Order.includes('shipments').where(['orders.state = ?', 'authorized']).where('shipments.id IS NULL')
You can also query on the association using the normal find syntax:
Order.find(:all, :include => "shipments", :conditions => ["orders.state = ? AND shipments.id IS NULL", "authorized"])
One option is to put a shipment_count on Order, where it will be automatically updated with the number of shipments you attach to it. Then you just
Order.all(:conditions => [:state => "authorized", :shipment_count => 0])
Alternatively, you can get your hands dirty with some SQL:
Order.find_by_sql("SELECT * FROM
(SELECT orders.*, count(shipments) AS shipment_count FROM orders
LEFT JOIN shipments ON orders.id = shipments.order_id
WHERE orders.status = 'authorized' GROUP BY orders.id)
AS order WHERE shipment_count = 0")
Test that prior to using it, as SQL isn't exactly my bag, but I think it's close to right. I got it to work for similar arrangements of objects on my production DB, which is MySQL.
Note that if you don't have an index on orders.status I'd strongly advise it!
What the query does: the subquery grabs all the order counts for all orders which are in authorized status. The outer query filters that list down to only the ones which have shipment counts equal to zero.
There's probably another way you could do it, a little counterintuitively:
"SELECT DISTINCT orders.* FROM orders
LEFT JOIN shipments ON orders.id = shipments.order_id
WHERE orders.status = 'authorized' AND shipments.id IS NULL"
Grab all orders which are authorized and don't have an entry in the shipments table ;)
This is going to work just fine if you're using Rails 6.1 or newer:
Order.where(state: 'authorized').where.missing(:shipments)