So in rails I use sqlite3 for development and mysql for production. Sqlite3 and mysql handle booleans differently ("t" or "f" in sqlite3 and true or false on mysql). Usually it's not a problem when I do a find because I can do this:
Comment.find(:all, :conditions => ["viewed = ?", false])
And rails will insert the appropriate value depending on environment. But what if I want to do a find_by_sql in which I need a boolean?