ruby - 3 (ruby connection to mysql )

require 'rubygems';
require 'mysql';
class ConnMysql
    attr_reader :conn;
    def initialize (host, user, pwd, db)
        @username = user;
        @password = pwd;
        @host = host;
        @db = db;
    end

    def connection
        @conn = Mysql.new(@host, @username, @password, @db);
    end

    def exequery sql
        st = @conn.prepare(sql);
        st.execute;
        return st.fetch;
    end
end

a = ConnMysql.new('localhost', 'root', 'livedoor2008', 'depot_development');
a.connection;
sql = "select * from users";
result = a.exequery(sql);
puts result.join(',');