Working With Rails

Why not just use the prepared statement? Just modify it like this:
:conditions => [ "common_given_names.name LIKE ?", "%#{keyword}%" ]

There are multiple examples in the Rails API documentation, for example here.

HTH

Clemens is right.

You should always use a prepared statement, otherwise you are setting yourself up for an SQL injection attack.
What would happen if the keyword variable contained “x’; DROP TABLE users;—” ?

Here’s a very good resource explaining SQL injection: http://www.unixwiz.net/techtips/sql-injection.html

Both Clemens and Jon give excellent advice. Also, note the ’%’ wildcard symbols that Clemens added. A LIKE statement is almost worthless without at least wildcarding the front, back or both ends of the search term. If you only needed exact matches then you should always opt for just using a standard ’=’ on an indexed field since LIKE statements can be a lot more expensive on most databases, causing a full table scan.