Q2
a)  SELECT coder_name,
TRUNC(months_between(sysdate, coder_date_of_birth)/12,0) Age
    FROM cd_attendee WHERE coder_phone IS NULL;

b)  SELECT coder_name, COUNT(*)
    FROM cd_attendee
    JOIN cd_attends USING (coder_id)
    GROUP BY coder_name HAVING COUNT(*)>2;

c)  SELECT DISTINCT organiser_name, loc_name
    FROM cd_organiser
    JOIN cd_coding_session USING (organiser_id)
    JOIN cd_location USING (loc_id);

Q3
a)  SELECT facilitator_name FROM cd_facilitator
    UNION
    SELECT organiser_name FROM cd_organiser;

b)  SELECT facilitator_name, facilitator_email
    FROM cd_facilitator
    MINUS
    SELECT organiser_name, organiser_email
    FROM cd_organiser;

c)  SELECT coder_name, badge_earned, spec_name
    FROM cd_attendee
    JOIN cd_attends USING (coder_id)
    JOIN cd_session_runs USING (s_start, loc_id, spec_code)
    JOIN cd_speciality USING (spec_code)
    WHERE badge_earned IS NOT NULL;