Get a Random Record from an ActiveRecord Model

Let's say you have an events table with a model name Event. If you want to get a random event from the table, you could run

Event.find_by_sql(
  <<-SQL
    SELECT * FROM events ORDER BY random() LIMIT 1
  SQL
).first

The functional part of this query is the ORDER BY random() bit. For every row that postgres is sorting, it generates a random number (between 0.0 and 1.0 by default). Then it sorts the rows by their randomly generated number. Read more about the postgres random() function at the documentation page.