On the Last Touch Query we can group by both utm_campaign and utm_source if we want

[jmcrey]

4. WITH last_touch AS (
    SELECT user_id,
           MAX(timestamp) as last_touch_at
    FROM page_visits
GROUP BY user_id),
lt_utm AS (
  SELECT lt.user_id,
              lt.last_touch_at,
             pv.utm_source,
            pv.utm_campaign
  FROM last_touch AS 'lt'
  JOIN page_visits AS 'pv'
  ON lt.user_id = pv.user_id
  AND lt.last_touch_at = pv.timestamp)
 SELECT COUNT(*),lt_utm.utm_campaign,
        lt_utm.utm_source
 FROM lt_utm
 GROUP BY 2
ORDER BY 1 DESC;

This is an excellent query that pulls together all the data we need in order to answer the question. I just wanted to point out that we can GROUP BY on both lt_utm.utm_campaign and lt_utm.utm_source for this query. So, we can change our GROUP BY clause to be:

GROUP BY 2, 3

Although this won't change the results of our output, it may clean up how the table is presented to us. But, this is just a note! The query is perfectly acceptable as it is.