text: /*
  
  Hopper Company Queries III Problem
  
  Description
  LeetCode Problem 1651.
  
  Table: Drivers
  
  +-------------+---------+
  | Column Name | Type    |
  +-------------+---------+
  | driver_id   | int     |
  | join_date   | date    |
  +-------------+---------+
  driver_id is the primary key for this table.
  Each row of this table contains the driver's ID and the date they joined the Hopper company.
  Table: Rides
  
  +--------------+---------+
  | Column Name  | Type    |
  +--------------+---------+
  | ride_id      | int     |
  | user_id      | int     |
  | requested_at | date    |
  +--------------+---------+
  ride_id is the primary key for this table.
  Each row of this table contains the ID of a ride, the user's ID that requested it, and the day they requested it.
  There may be some ride requests in this table that were not accepted.
  Table: AcceptedRides
  
  +---------------+---------+
  | Column Name   | Type    |
  +---------------+---------+
  | ride_id       | int     |
  | driver_id     | int     |
  | ride_distance | int     |
  | ride_duration | int     |
  +---------------+---------+
  ride_id is the primary key for this table.
  Each row of this table contains some information about an accepted ride.
  It is guaranteed that each accepted ride exists in the Rides table.
  Write an SQL query to compute the average_ride_distance and average_ride_duration of every 3-month window starting from January - March 2020 to October - December 2020. Round average_ride_distance and average_ride_duration to the nearest two decimal places.
  
  The average_ride_distance is calculated by summing up the total ride_distance values from the three months and dividing it by 3. The average_ride_duration is calculated in a similar way.
  
  Return the result table ordered by month in ascending order, where month is the starting month’s number (January is 1, February is 2, etc.).
  
  The query result format is in the following example.
  
  Drivers table:
  +-----------+------------+
  | driver_id | join_date  |
  +-----------+------------+
  | 10        | 2019-12-10 |
  | 8         | 2020-1-13  |
  | 5         | 2020-2-16  |
  | 7         | 2020-3-8   |
  | 4         | 2020-5-17  |
  | 1         | 2020-10-24 |
  | 6         | 2021-1-5   |
  +-----------+------------+
  
  Rides table:
  +---------+---------+--------------+
  | ride_id | user_id | requested_at |
  +---------+---------+--------------+
  | 6       | 75      | 2019-12-9    |
  | 1       | 54      | 2020-2-9     |
  | 10      | 63      | 2020-3-4     |
  | 19      | 39      | 2020-4-6     |
  | 3       | 41      | 2020-6-3     |
  | 13      | 52      | 2020-6-22    |
  | 7       | 69      | 2020-7-16    |
  | 17      | 70      | 2020-8-25    |
  | 20      | 81      | 2020-11-2    |
  | 5       | 57      | 2020-11-9    |
  | 2       | 42      | 2020-12-9    |
  | 11      | 68      | 2021-1-11    |
  | 15      | 32      | 2021-1-17    |
  | 12      | 11      | 2021-1-19    |
  | 14      | 18      | 2021-1-27    |
  +---------+---------+--------------+
  
  AcceptedRides table:
  +---------+-----------+---------------+---------------+
  | ride_id | driver_id | ride_distance | ride_duration |
  +---------+-----------+---------------+---------------+
  | 10      | 10        | 63            | 38            |
  | 13      | 10        | 73            | 96            |
  | 7       | 8         | 100           | 28            |
  | 17      | 7         | 119           | 68            |
  | 20      | 1         | 121           | 92            |
  | 5       | 7         | 42            | 101           |
  | 2       | 4         | 6             | 38            |
  | 11      | 8         | 37            | 43            |
  | 15      | 8         | 108           | 82            |
  | 12      | 8         | 38            | 34            |
  | 14      | 1         | 90            | 74            |
  +---------+-----------+---------------+---------------+
  
  Result table:
  +-------+-----------------------+-----------------------+
  | month | average_ride_distance | average_ride_duration |
  +-------+-----------------------+-----------------------+
  | 1     | 21.00                 | 12.67                 |
  | 2     | 21.00                 | 12.67                 |
  | 3     | 21.00                 | 12.67                 |
  | 4     | 24.33                 | 32.00                 |
  | 5     | 57.67                 | 41.33                 |
  | 6     | 97.33                 | 64.00                 |
  | 7     | 73.00                 | 32.00                 |
  | 8     | 39.67                 | 22.67                 |
  | 9     | 54.33                 | 64.33                 |
  | 10    | 56.33                 | 77.00                 |
  +-------+-----------------------+-----------------------+
  
  By the end of January --> average_ride_distance = (0+0+63)/3=21, average_ride_duration = (0+0+38)/3=12.67
  By the end of February --> average_ride_distance = (0+63+0)/3=21, average_ride_duration = (0+38+0)/3=12.67
  By the end of March --> average_ride_distance = (63+0+0)/3=21, average_ride_duration = (38+0+0)/3=12.67
  By the end of April --> average_ride_distance = (0+0+73)/3=24.33, average_ride_duration = (0+0+96)/3=32.00
  By the end of May --> average_ride_distance = (0+73+100)/3=57.67, average_ride_duration = (0+96+28)/3=41.33
  By the end of June --> average_ride_distance = (73+100+119)/3=97.33, average_ride_duration = (96+28+68)/3=64.00
  By the end of July --> average_ride_distance = (100+119+0)/3=73.00, average_ride_duration = (28+68+0)/3=32.00
  By the end of August --> average_ride_distance = (119+0+0)/3=39.67, average_ride_duration = (68+0+0)/3=22.67
  By the end of Septemeber --> average_ride_distance = (0+0+163)/3=54.33, average_ride_duration = (0+0+193)/3=64.33
  By the end of October --> average_ride_distance = (0+163+6)/3=56.33, average_ride_duration = (0+193+38)/3=77.00
  
  */
  
  
  
  # V0
  
  # V1
  # https://circlecoder.com/hopper-company-queries-III/
  select month,
      coalesce(round(sum(ride_distance)/3,2),0) as average_ride_distance,
      coalesce(round(sum(ride_duration)/3,2),0) as average_ride_duration
  from
  (
      select months.month, ride_id
      from Rides
      right join
      (
          select "2020-1-1" as start, "2020-3-31" as last, 1 as month
          union select "2020-2-1", "2020-4-30", 2
          union select "2020-3-1", "2020-5-31", 3
          union select "2020-4-1", "2020-6-30", 4
          union select "2020-5-1", "2020-7-31", 5
          union select "2020-6-1", "2020-8-31", 6
          union select "2020-7-1", "2020-9-30", 7
          union select "2020-8-1", "2020-10-31", 8
          union select "2020-9-1", "2020-11-30", 9
          union select "2020-10-1", "2020-12-31", 10
      ) as months
      on months.start <= requested_at and months.last >= requested_at
  ) total
  left join AcceptedRides as a
  on total.ride_id=a.ride_id
  group by month
  order by month
  
  # V2
  # Time:  O(d + r + tlogt)
  # Space: O(d + r + t)
  WITH RECURSIVE year_cte AS (
      SELECT MIN(YEAR(join_date)) year,
             MAX(YEAR(join_date)) max_year
      FROM drivers
      UNION ALL
      SELECT year + 1,
             max_year
      FROM year_cte
      WHERE year < max_year
  ),
  year_month_cte AS (
      SELECT year,
             1 month,
             12 max_month
      FROM year_cte
      UNION ALL
      SELECT year,
             month + 1,
             max_month
      FROM year_month_cte
      WHERE month < max_month
  ),
  total_per_month_cte AS (
      SELECT MAX(YEAR(r.requested_at)) 'year',
             MAX(MONTH(r.requested_at)) 'month',
             SUM(a.ride_distance) AS monthly_distance,
             SUM(a.ride_duration) AS monthly_duration
      FROM rides r LEFT JOIN acceptedrides a ON r.ride_id = a.ride_id
      GROUP BY LEFT(r.requested_at, 7)
  )
  SELECT month,
         average_ride_distance,
         average_ride_duration
  FROM (
      SELECT t1.year,
             t1.month,
             ROUND(IFNULL(SUM(t2.monthly_distance) OVER w, 0)/3, 2) average_ride_distance, 
             ROUND(IFNULL(SUM(t2.monthly_duration) OVER w, 0)/3, 2) average_ride_duration
      FROM year_month_cte t1
           LEFT JOIN total_per_month_cte t2 ON t1.year = t2.year AND t1.month = t2.month
           WINDOW w AS (ORDER BY t1.year, t1.month ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING)
  ) tmp
  WHERE year = 2020 AND month <= 10;