Debug info: Unknown column 'username' in 'where clause'
SELECT id
FROM mdl_questionnaire_response
WHERE complete = 'y'
AND username = ?
AND survey_id = ? LIMIT 0, 1
[array (
0 => '2',
1 => '2',
)]
The username field in questionnaire_response was changed to userid in release 3.3.0. What version are you using? It would seem that somehow your code might be older than your database.