嵌入式Linux驱动开发（LCD屏幕专题）（四）

数据准备

Create table If Not Exists Actions (user_id int, post_id int, action_date date, action ENUM('view', 'like', 'reaction', 'comment', 'report', 'share'), extra varchar(10));
Truncate table Actions;
insert into Actions (user_id, post_id, action_date, action, extra) values ('1', '1', '2019-07-01', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('1', '1', '2019-07-01', 'like', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('1', '1', '2019-07-01', 'share', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('2', '4', '2019-07-04', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('2', '4', '2019-07-04', 'report', 'spam');
insert into Actions (user_id, post_id, action_date, action, extra) values ('3', '4', '2019-07-04', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('3', '4', '2019-07-04', 'report', 'spam');
insert into Actions (user_id, post_id, action_date, action, extra) values ('4', '3', '2019-07-02', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('4', '3', '2019-07-02', 'report', 'spam');
insert into Actions (user_id, post_id, action_date, action, extra) values ('5', '2', '2019-07-04', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('5', '2', '2019-07-04', 'report', 'racism');
insert into Actions (user_id, post_id, action_date, action, extra) values ('5', '5', '2019-07-04', 'view', 'None');
insert into Actions (user_id, post_id, action_date, action, extra) values ('5', '5', '2019-07-04', 'report', 'racism');

需求

编写一条SQL，查询每种报告理由（report reason）在昨天的不同报告数量（post_id）。假设今天是2019-07-05。

输入

输出

with t1 as (
    select distinct post_id,extra
    from Actions
    where action='report' and action_date='2019-07-04'
)
select extra as  report_reason,count(1) as report_count
from t1
group by extra
;