解答

182

SQL文(クエリ)

SELECT
  prefecture
  , SUM(p) AS premium_users
  , COUNT(DISTINCT user_id) AS users
  , SUM(p) / COUNT(DISTINCT user_id) AS premium_rate
FROM
  (
    SELECT
      prefecture
      , user_id
      , IF(is_premium IS TRUE, 1, 0) AS p
    FROM
      sample.customers
  )
GROUP BY
  prefecture
ORDER BY
  2 DESC
LIMIT 3

結果テーブル

結果テーブル

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