SQL LENGTH in ActiveRecord?

How can I translate this MySQL's WHERE to ActiveRecord :condit开发者_StackOverflowion?

 SELECT * FROM users WHERE LENGTH(users.last_name) < 3

Thanks!

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User.find(:all, :conditions => ["LENGTH(last_name) < ?", 3])

or you can use find_by_sql

 User.find_by_sql("SELECT * FROM users WHERE LENGTH(users.last_name) < 3")