Should I check for errors after DB updates ?

[eluser]flaviog[/eluser]
I am currently checking for errors after I modify data in my DB. At the end of each of my functions in my models, I check if changes occured with a if ($this->db->affected_rows())

Should I be doing this, or does CodeIgniter's Database Class already verify for errors and I did not find about it ? If it does, how can I check for errors ?

Thank you.