Ruby rails - select only few columns from the data base
Ruby on-RailsRubyRuby on-Rails-3Rails ActiverecordRuby on-Rails Problem Overview
What is the way in rails to structure sql query to only select certain columns from the database, I have some large data fields which I want to avoid loading from continuous periodic ajax calls. Reading unnecessarily is resource consuming and slow.
@itemlist = Item.find(:all, :conditions => { .... } ) #this select all columns
I am looking for SELECT name, address FROM users; instead of SELECT * FROM users;
Ruby on-Rails Solutions
Solution 1 - Ruby on-Rails
Rails 3:
Item.select("name, address").where( .... )
Solution 2 - Ruby on-Rails
Make use of :select construct. Try this:
@itemlist = Item.select('name, address', conditions: { .... } )
For previous version of Rails:
@itemlist = Item.find(:all,:select => 'name, address', :conditions => { .... } )
Solution 3 - Ruby on-Rails
Using Arel (aka in Rails 3), use:
Item.where(...).select("name, address")
Also, it seems .select gets ignored if you tack on a scope that has an :include => ...
Solution 4 - Ruby on-Rails
@itemlist = Item.select('name, address').where(...#some condition)
Solution 5 - Ruby on-Rails
If want to select specific columns from the rails console, pluck( will work.
Example:
2.4.1 :007 > User.connection
2.4.1 :006 > User.all.pluck(:email)
(0.3ms) SELECT `users`.`email` FROM `users`
=> ["[email protected]", "[email protected]"]
Note that this will also work from within the Rails app.
Solution 6 - Ruby on-Rails
Try this:
@itemlist = Item.find(:all, :select => "name, address", :conditions => { .... } )