プログラムで月間ページビューを取得する方法は?できればData Explorerを使用

はい、可能です。この場合、まず日付フィールドの形式を調整し、その後でグループ化を調整する必要があります。以下は調整済みのクエリです。

-- [params]
-- date :start_date
-- date :end_date

WITH data AS 
    (SELECT
        date_part('month', ar.date) AS month,
        date_part('year', ar.date) AS year,
        CASE 
          WHEN ar.req_type=6 THEN 'Crawlers'
          WHEN ar.req_type=7 THEN 'Logged in users'
          WHEN ar.req_type=8 THEN 'Anonymous users'
        END AS pageview,
        ar.count AS views
    FROM application_requests ar
    WHERE req_type IN (6,7,8)
        AND ar.date::date BETWEEN :start_date::date
        AND :end_date::date
    ORDER BY ar.date ASC, ar.req_type
    )
    
  SELECT 
    month, 
    year, 
    sum(views) AS qtt_views
  FROM  data 
  GROUP BY year, month
  ORDER BY year DESC, month ASC
month year count
1 2021 1000
2 2021 500
1 2020 1500
2 2020 2000
3 2020 2500