1113. Reported Posts

https://leetcode.com/problems/reported-posts

Description

Table: Actions

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| user\_id       | int     |
| post\_id       | int     |
| action\_date   | date    | 
| action        | enum    |
| extra         | varchar |
+---------------+---------+
There is no primary key for this table, it may have duplicate rows.
The action column is an ENUM type of ('view', 'like', 'reaction', 'comment', 'report', 'share').
The extra column has optional information about the action such as a reason for report or a type of reaction. 

Write an SQL query that reports the number of posts reported yesterday for each report reason. Assume today is 2019-07-05.

The query result format is in the following example:

Actions table:
+---------+---------+-------------+--------+--------+
| 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       | 4       | 2019-07-04  | view   | null   |
| 2       | 4       | 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       | 2019-07-04  | view   | null   |
| 5       | 2       | 2019-07-04  | report | racism |
| 5       | 5       | 2019-07-04  | view   | null   |
| 5       | 5       | 2019-07-04  | report | racism |
+---------+---------+-------------+--------+--------+
Result table:
+---------------+--------------+
| report\_reason | report\_count |
+---------------+--------------+
| spam          | 1            |
| racism        | 2            |
+---------------+--------------+ 
Note that we only care about report reasons with non zero number of reports.

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