Rails Include Only Selected Columns from Relation

ActiveRecord includes. Specify included columns

Rails doesn't have the facility to pass the options for include query. But we can pass these params with the association declaration under the model.

For your scenario, you need to create a new association with users model under the profile model, like below

belongs_to :user_only_fetch_email, :select => "users.id, users.email", :class_name => "User"

I just created one more association but it points to User model only. So your query will be,

Profile.includes(:user_only_fetch_email)

or

Profile.includes(:user_only_fetch_email).find(some_profile_ids)

ActiveRecord find and only return selected columns

In Rails 2

l = Location.find(:id => id, :select => "name, website, city", :limit => 1)

...or...

l = Location.find_by_sql(:conditions => ["SELECT name, website, city FROM locations WHERE id = ? LIMIT 1", id])

This reference doc gives you the entire list of options you can use with .find, including how to limit by number, id, or any other arbitrary column/constraint.

In Rails 3 w/ActiveRecord Query Interface

l = Location.where(["id = ?", id]).select("name, website, city").first

Ref: Active Record Query Interface

You can also swap the order of these chained calls, doing .select(...).where(...).first - all these calls do is construct the SQL query and then send it off.

Rails 3 Joins -- Select only certain columns

You could use something like this:

@comments = Comment.joins(:user)
                   .select("comments.*, users.first_name")
                   .where(study_id: @study.id)

How to select only specific columns when querying using ActiveRecord?

In your post model you can define the association as follows:

belongs_to :user, :select => [:username]

Then referring to the user via a post would select only the stated columns.

Retrieving only certain columns with Rails 3 where clause

results = Model.where(:lat => (south..north), :lng => (east..west)).select([:lat, :long, :id])

You'll also probably want to include the :id in that select if you want your results to behave like reasonable ActiveRecord objects.

Edit: Select takes a single arg, can be an array.

ActiveRecord select except columns

write a scope like

def select_without columns
  select(column_names - columns.map(&:to_s))
end

in Rails how to select additional columns from multiple tables

result = User.first.usertags.joins(:tag).select("tags.name as tag_name, tags.id, usertags.id, user.id")

result.collect{|r| r.tag_name}

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