LeetCode:Database 55.レポートのレコードII

要求:SQLを作成して検索します:ゴミ広告として報告された投稿の中で、削除された投稿の毎日の平均割合は、小数点以下2位に四捨五入されます.
Actionsテーブルの構造:

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| user_id       | int     |
| post_id       | int     |
| action_date   | date    |
| action        | enum    |
| extra         | varchar |
+---------------+---------+
       ，          。

Removalsテーブルの構造:

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| post_id       | int     |
| remove_date   | date    | 
+---------------+---------+
        post_id。

Actionsテーブル:

+---------+---------+-------------+--------+--------+
| user_id | post_id | action_date | action | extra  |
+---------+---------+-------------+--------+--------+
| 1       | 1       | 2019-07-01  | view   | null   |
| 1       | 1       | 2019-07-01  | like   | null   |
| 1       | 1       | 2019-07-01  | share  | null   |
| 2       | 2       | 2019-07-04  | view   | null   |
| 2       | 2       | 2019-07-04  | report | spam   |
| 3       | 4       | 2019-07-04  | view   | null   |
| 3       | 4       | 2019-07-04  | report | spam   |
| 4       | 3       | 2019-07-02  | view   | null   |
| 4       | 3       | 2019-07-02  | report | spam   |
| 5       | 2       | 2019-07-03  | view   | null   |
| 5       | 2       | 2019-07-03  | report | racism |
| 5       | 5       | 2019-07-03  | view   | null   |
| 5       | 5       | 2019-07-03  | report | racism |
+---------+---------+-------------+--------+--------+

Removalsテーブル:

+---------+-------------+
| post_id | remove_date |
+---------+-------------+
| 2       | 2019-07-20  |
| 3       | 2019-07-18  |
+---------+-------------+

Result Table:

+-----------------------+
| average_daily_percent |
+-----------------------+
| 75.00                 |
+-----------------------+
2019-07-04           50%，               ，         。
2019-07-02           100%，                    。
               ，      ：(50 + 100) / 2 = 75%
  ，            ，             。

SQL文:注意:onは左外の表と右外の表に対して無効で、whereフィルタリングを使用する必要があります

#1.  1
SELECT ROUND(AVG(c1)*100,2) AS average_daily_percent
FROM( 
SELECT COUNT(IFNULL(DISTINCT b.post_id,0))/COUNT(DISTINCT a.post_id) AS c1,a.action_date AS d1
FROM a  
JOIN a b
ON a.action_date=b.action_date AND b.post_id IN(SELECT post_id FROM removals)  
GROUP BY a.action_date)c

#2.  2
select round(avg(c1)*100,2) as average_daily_percent
from(
select count(distinct a2.post_id)/count(distinct a1.post_id) as c1
from actions as a1
left join actions as a2
on a1.action_date=a2.action_date
and a2.post_id in(select post_id from removals)
where a1.extra='spam'
group by a1.action_date)b;