DECLARE
   FUNCTION random_question_query (
      user_id_in         IN INTEGER,
      domain_id_in       IN INTEGER DEFAULT NULL,
      topic_id_in        IN INTEGER DEFAULT NULL,
      difficulty_id_in   IN INTEGER DEFAULT NULL,
      filter_in          IN VARCHAR2 DEFAULT NULL,
      unplayed_in        IN BOOLEAN DEFAULT TRUE)
      RETURN VARCHAR2
   IS
      l_query          qdb_config.maxvarchar2
         := 'SELECT question_id FROM (SELECT question_id FROM dg_training_questions_v tq';
      l_domain_count   INTEGER;
      l_cur            SYS_REFCURSOR;

      l_selected       INTEGER;
   BEGIN
      SELECT COUNT (*)
        INTO l_domain_count
        FROM qdb_user_domains
       WHERE user_id = user_id_in;

      l_query :=
            l_query
         || CASE
               WHEN domain_id_in IS NULL AND topic_id_in IS NULL
               THEN
                  CASE
                     WHEN l_domain_count > 0
                     THEN
                           ' WHERE domain_id IN (SELECT domain_id FROM qdb_user_domains WHERE user_id = '
                        || user_id_in
                        || ')'
                  END
               WHEN topic_id_in IS NOT NULL
               THEN
                     ' WHERE tq.topic_id IN (SELECT t2.topic_id from qdb_topics t2'
                  || ' CONNECT BY prior t2.topic_id = t2.parent_topic_id START WITH t2.topic_id = '
                  || topic_id_in
                  || ')'
               WHEN domain_id_in IS NOT NULL
               THEN
                  ' WHERE domain_id = ' || domain_id_in
            END
         || CASE
               WHEN difficulty_id_in IS NOT NULL
               THEN
                  ' AND difficulty_id = ' || difficulty_id_in
            END
         || CASE
               WHEN filter_in IS NOT NULL
               THEN
                  /* Find questions with topics whose names match. */
                  ' AND UPPER (tq.topic) LIKE ''%'' || upper (filter_in) || ''%'''
            END;

      l_query :=
            l_query
         || CASE
               WHEN unplayed_in
               THEN
                     'MINUS SELECT z.question_id FROM qdb_quizzes z, qdb_compev_answers a'
                  || ' WHERE a.user_id = '
                  || user_id_in
                  || 'AND z.comp_event_id = a.comp_event_id'
            END
         || ') ORDER BY DBMS_RANDOM.VALUE ()';
      RETURN l_query;
   END;
BEGIN
   NULL;
END;