Ruby on Rails 3 howto make 'OR' condition

问题:

I need an SQL statement that check if one condition is satisfied:

SELECT * FROM my_table WHERE my_table.x=1 OR my_table.y=1

I want to do this the 'Rails 3' way. I was looking for something like:

Account.where(:id => 1).or.where(:id => 2)

I know that I can always fallback to sql or a conditions string. However, in my experience this often leads to chaos when combining scopes. What is the best way to do this?

Another related question, is how can describe relationship that depends on an OR condition. The only way I found:

has_many :my_thing, :class_name => "MyTable",  :finder_sql => 'SELECT my_tables.* ' + 'FROM my_tables ' +
'WHERE my_tables.payer_id = #{id} OR my_tables.payee_id = #{id}'

However, these again breaks when used in combinations. IS there a better way to specify this?

回答1:

Sadly, the .or isn't implemented yet (but when it is, it'll be AWESOME).

So you'll have to do something like:

class Project < ActiveRecord::Base
  scope :sufficient_data, :conditions=>['ratio_story_completion != 0 OR ratio_differential != 0']
  scope :profitable, :conditions=>['profit > 0']

That way you can still be awesome and do:

Project.sufficient_data.profitable

回答2:

Account.where(id: [1,2]) no explanation needed.

回答3:

This will works in Rails 5, see rails master :

Post.where('id = 1').or(Post.where('id = 2'))
# => SELECT * FROM posts WHERE (id = 1) OR (id = 2)

For Rails 3.0.4+:

accounts = Account.arel_table
Account.where(accounts[:id].eq(1).or(accounts[:id].eq(2)))

回答4:

Those arel queries are unreadable to me.

What's wrong with a SQL string? In fact, the Rails guides exposes this way as the first way to make conditions in queries: http://guides.rubyonrails.org/active_record_querying.html#array-conditions

So, I bet for this way to do it as the "Rails way":

Account.where("id = 1 OR id = 2")

In my humble opinion, it's shorter and clearer.

回答5:

I'd go with the IN clause, e.g:

Account.where(["id in (?)", [1, 2]])

回答6:

I've used the Squeel gem (https://github.com/ernie/squeel/) to do OR queries and it works beautifully.

It lets you write your query as Account.where{(id == 1) | (id == 2)}

回答7:

You can define an Array as value in the :conditions Hash.

So you could do for example:

Account.all(:conditions => { :id => [1, 2] })

Tested with Rails 3.1.0

回答8:

Alternate syntax using Hash

Account.where("id = :val1 OR id = :val2", val1: 1, val2: 2).

This is particularly useful, when the value is compared with multiple columns. eg:

User.where("first_name = :name OR last_name = :name", name: 'tom')

回答9:

With rails_or, you could do it like:

Account.where(id: 1).or(id: 2)

(It works in Rails 4 and 5, too.)