数据库系统原理与应用教程（077）—— MySQL 练习题：操作题 168-172（二十一）：综合练习

168、分组统计（1）

该题目使用的表和数据如下：

/*
DROP TABLE IF EXISTS tb_user_video_log, tb_video_info;
CREATE TABLE tb_user_video_log (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',uid INT NOT NULL COMMENT '用户ID',video_id INT NOT NULL COMMENT '视频ID',start_time datetime COMMENT '开始观看时间',end_time datetime COMMENT '结束观看时间',if_follow TINYINT COMMENT '是否关注',if_like TINYINT COMMENT '是否点赞',if_retweet TINYINT COMMENT '是否转发',comment_id INT COMMENT '评论ID'
) CHARACTER SET utf8 COLLATE utf8_bin;CREATE TABLE tb_video_info (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',video_id INT UNIQUE NOT NULL COMMENT '视频ID',author INT NOT NULL COMMENT '创作者ID',tag VARCHAR(16) NOT NULL COMMENT '类别标签',duration INT NOT NULL COMMENT '视频时长(秒数)',release_time datetime NOT NULL COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_bin;INSERT INTO tb_user_video_log(uid, video_id, start_time, end_time, if_follow, if_like, if_retweet, comment_id) VALUES(101, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:30', 0, 1, 1, null),(102, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:24', 0, 0, 1, null),(103, 2001, '2021-10-01 11:00:00', '2021-10-01 11:00:34', 0, 1, 0, 1732526),(101, 2002, '2021-09-01 10:00:00', '2021-09-01 10:00:42', 1, 0, 1, null),(102, 2002, '2021-10-01 11:00:00', '2021-10-01 11:00:30', 1, 0, 1, null);INSERT INTO tb_video_info(video_id, author, tag, duration, release_time) VALUES(2001, 901, '影视', 30, '2021-01-01 7:00:00'),(2002, 901, '美食', 60, '2021-01-01 7:00:00'),(2003, 902, '旅游', 90, '2021-01-01 7:00:00');*/

用户-视频互动表：tb_user_video_log（uid：用户ID, video_id：视频ID, start_time：开始观看时间，end_time：结束观看时间，if_follow：是否关注，if_like：是否点赞，if_retweet：是否转发，comment_id：评论ID），表中数据如下：

mysql> select * from tb_user_video_log;
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
| id | uid | video_id | start_time  | end_time  | if_follow | if_like | if_retweet | comment_id |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
|  1 | 101 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:30 |    0 |   1 |   1 |    NULL |
|  2 | 102 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:24 |    0 |   0 |   1 |    NULL |
|  3 | 103 |     2001 | 2021-10-01 11:00:00 | 2021-10-01 11:00:34 |    0 |   1 |   0 | 1732526 |
|  4 | 101 |     2002 | 2021-09-01 10:00:00 | 2021-09-01 10:00:42 |    1 |   0 |   1 |    NULL |
|  5 | 102 |     2002 | 2021-10-01 11:00:00 | 2021-10-01 11:00:30 |    1 |   0 |   1 |    NULL |
+----+-----+----------+---------------------+----------+-----------+---------+-----------------+
5 rows in set (0.03 sec)

短视频信息表：tb_video_info（video_id：视频ID，author：创作者ID，tag：类别标签，duration：视频时长（秒）， release_time：发布时间），表中数据如下：

mysql> select * from tb_video_info;
+----+----------+--------+--------+----------+---------------------+
| id | video_id | author | tag    | duration | release_time        |
+----+----------+--------+--------+----------+---------------------+
|  1 |     2001 |    901 | 影视   |       30 | 2021-01-01 07:00:00 |
|  2 |     2002 |    901 | 美食   |       60 | 2021-01-01 07:00:00 |
|  3 |     2003 |    902 | 旅游   |       90 | 2021-01-01 07:00:00 |
+----+----------+--------+--------+----------+---------------------+
3 rows in set (0.00 sec)

【问题】计算 2021 年有播放记录的每个视频的完播率（结果保留三位小数），按完播率降序排序。

说明：视频完播率是指完成播放次数占总播放次数的比例。即：结束观看时间与开始播放时间的差 >= 视频时长，视为完成播放。

查询结果如下：

video_id avg_comp_play_rate
2001 0.667
2002 0.000

解答：

/*
select b.video_id, round(ifnull(a.finish_cnt, 0)/b.cnt, 3) avg_comp_play_rate
from (select tu.video_id, count(*) finish_cntfrom tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_idwhere year(start_time) = 2021 and right(timediff(end_time, start_time),2) + substr(timediff(end_time, start_time),4,2)*60 >= tv.durationgroup by tu.video_id) a right join(select video_id, count(*) cntfrom tb_user_video_loggroup by video_id) bon a.video_id = b.video_id
order by avg_comp_play_rate desc;
*/
mysql> select b.video_id, round(ifnull(a.finish_cnt, 0)/b.cnt, 3) avg_comp_play_rate-> from (select tu.video_id, count(*) finish_cnt->       from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id->       where year(start_time) = 2021 and ->       right(timediff(end_time, start_time),2) + substr(timediff(end_time, start_time),4,2)*60 ->       >= tv.duration->       group by tu.video_id) a right join->       (select video_id, count(*) cnt->        from tb_user_video_log->        group by video_id) b->        on a.video_id = b.video_id-> order by avg_comp_play_rate desc;
+----------+--------------------+
| video_id | avg_comp_play_rate |
+----------+--------------------+
|     2001 |              0.667 |
|     2002 |              0.000 |
+----------+--------------------+
2 rows in set (0.00 sec)

169、分组统计（2）

该题目使用的表和数据如下：

/*
DROP TABLE IF EXISTS tb_user_video_log, tb_video_info;
CREATE TABLE tb_user_video_log (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',uid INT NOT NULL COMMENT '用户ID',video_id INT NOT NULL COMMENT '视频ID',start_time datetime COMMENT '开始观看时间',end_time datetime COMMENT '结束观看时间',if_follow TINYINT COMMENT '是否关注',if_like TINYINT COMMENT '是否点赞',if_retweet TINYINT COMMENT '是否转发',comment_id INT COMMENT '评论ID'
) CHARACTER SET utf8 COLLATE utf8_bin;CREATE TABLE tb_video_info (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',video_id INT UNIQUE NOT NULL COMMENT '视频ID',author INT NOT NULL COMMENT '创作者ID',tag VARCHAR(16) NOT NULL COMMENT '类别标签',duration INT NOT NULL COMMENT '视频时长(秒数)',release_time datetime NOT NULL COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_bin;INSERT INTO tb_user_video_log(uid, video_id, start_time, end_time, if_follow, if_like, if_retweet, comment_id) VALUES(101, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:30', 0, 1, 1, null),(102, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:21', 0, 0, 1, null),(103, 2001, '2021-10-01 11:00:50', '2021-10-01 11:01:20', 0, 1, 0, 1732526),(102, 2002, '2021-10-01 11:00:00', '2021-10-01 11:00:30', 1, 0, 1, null),(103, 2002, '2021-10-01 10:59:05', '2021-10-01 11:00:05', 1, 0, 1, null);INSERT INTO tb_video_info(video_id, author, tag, duration, release_time) VALUES(2001, 901, '影视', 30, '2021-01-01 7:00:00'),(2002, 901, '美食', 60, '2021-01-01 7:00:00'),(2003, 902, '旅游', 90, '2020-01-01 7:00:00');
*/

用户-视频互动表：tb_user_video_log（uid：用户ID, video_id：视频ID, start_time：开始观看时间，end_time：结束观看时间，if_follow：是否关注，if_like：是否点赞，if_retweet：是否转发，comment_id：评论ID），表中数据如下：

mysql> select * from tb_user_video_log;
+----+-----+----------+---------------------+---------------------+-----------+---------+-------+
| id | uid | video_id | start_time  | end_time   | if_follow | if_like | if_retweet | comment_id |
+----+-----+----------+---------------------+---------------------+-----------+---------+-------+
|  1 | 101 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:30 |  0 |  1 |   1 |    NULL |
|  2 | 102 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:21 |  0 |  0 |   1 |    NULL |
|  3 | 103 |     2001 | 2021-10-01 11:00:50 | 2021-10-01 11:01:20 |  0 |  1 |   0 | 1732526 |
|  4 | 102 |     2002 | 2021-10-01 11:00:00 | 2021-10-01 11:00:30 |  1 |  0 |   1 |    NULL |
|  5 | 103 |     2002 | 2021-10-01 10:59:05 | 2021-10-01 11:00:05 |  1 |  0 |   1 |    NULL |
+----+-----+----------+---------------------+---------------------+-----------+---------+-------+
5 rows in set (0.00 sec)

短视频信息表：tb_video_info（video_id：视频ID，author：创作者ID，tag：类别标签，duration：视频时长（秒）， release_time：发布时间），表中数据如下：

mysql> select * from tb_video_info;
+----+----------+--------+--------+----------+---------------------+
| id | video_id | author | tag    | duration | release_time        |
+----+----------+--------+--------+----------+---------------------+
|  1 |     2001 |    901 | 影视   |       30 | 2021-01-01 07:00:00 |
|  2 |     2002 |    901 | 美食   |       60 | 2021-01-01 07:00:00 |
|  3 |     2003 |    902 | 旅游   |       90 | 2020-01-01 07:00:00 |
+----+----------+--------+--------+----------+---------------------+
3 rows in set (0.00 sec)

【问题】计算各类视频的平均播放进度，将进度大于 60% 的类别输出。

说明：

（1）播放进度 = 播放时长 ÷ 视频时长 * 100%，当播放时长大于视频时长时，播放进度均记为 100%。

（2）结果保留两位小数，并按播放进度倒序排序。

查询结果如下：

tag avg_play_progress
影视 90.00%
美食 75.00%

解答：

/*
select tv.tag, concat(round( avg( if((right(timediff(tu.end_time, tu.start_time),2) + substr(timediff(tu.end_time, tu.start_time),4,2)*60) / tv.duration >= 1, 1,(right(timediff(tu.end_time, tu.start_time),2) + substr(timediff(tu.end_time, tu.start_time),4,2)*60) / tv. duration) * 100), 2),'%') avg_play_progress
from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id
group by tv.tag having avg_play_progress > '60.00%'
order by avg_play_progress desc;
*/
mysql> select tv.tag, concat(round( avg( ->        if(->            (right(timediff(tu.end_time, tu.start_time),2) + ->             substr(timediff(tu.end_time, tu.start_time),4,2)*60->            ) / tv.duration >= 1, 1,->            (right(timediff(tu.end_time, tu.start_time),2) + ->             substr(timediff(tu.end_time, tu.start_time),4,2)*60) / tv. duration->            ) * 100->         ), 2),'%') avg_play_progress -> from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id-> group by tv.tag having avg_play_progress > '60.00%'-> order by avg_play_progress desc;
+--------+-------------------+
| tag    | avg_play_progress |
+--------+-------------------+
| 影视   | 90.00%            |
| 美食   | 75.00%            |
+--------+-------------------+
2 rows in set (0.00 sec)

170、分组统计（3）

该题目使用的表和数据如下：

/*
DROP TABLE IF EXISTS tb_user_video_log, tb_video_info;
CREATE TABLE tb_user_video_log (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',uid INT NOT NULL COMMENT '用户ID',video_id INT NOT NULL COMMENT '视频ID',start_time datetime COMMENT '开始观看时间',end_time datetime COMMENT '结束观看时间',if_follow TINYINT COMMENT '是否关注',if_like TINYINT COMMENT '是否点赞',if_retweet TINYINT COMMENT '是否转发',comment_id INT COMMENT '评论ID'
) CHARACTER SET utf8 COLLATE utf8_bin;CREATE TABLE tb_video_info (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',video_id INT UNIQUE NOT NULL COMMENT '视频ID',author INT NOT NULL COMMENT '创作者ID',tag VARCHAR(16) NOT NULL COMMENT '类别标签',duration INT NOT NULL COMMENT '视频时长(秒数)',release_time datetime NOT NULL COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_bin;INSERT INTO tb_user_video_log(uid, video_id, start_time, end_time, if_follow, if_like, if_retweet, comment_id) VALUES(101, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:20', 0, 1, 1, null),(102, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:15', 0, 0, 1, null),(103, 2001, '2021-10-01 11:00:50', '2021-10-01 11:01:15', 0, 1, 0, 1732526),(102, 2002, '2021-09-10 11:00:00', '2021-09-10 11:00:30', 1, 0, 1, null),(103, 2002, '2021-10-01 10:59:05', '2021-10-01 11:00:05', 1, 0, 0, null);INSERT INTO tb_video_info(video_id, author, tag, duration, release_time) VALUES(2001, 901, '影视', 30, '2021-01-01 7:00:00'),(2002, 901, '美食', 60, '2021-01-01 7:00:00'),(2003, 902, '旅游', 90, '2020-01-01 7:00:00');*/

用户-视频互动表：tb_user_video_log（uid：用户ID, video_id：视频ID, start_time：开始观看时间，end_time：结束观看时间，if_follow：是否关注，if_like：是否点赞，if_retweet：是否转发，comment_id：评论ID），表中数据如下：

mysql> select * from tb_user_video_log;
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
| id | uid | video_id | start_time    | end_time | if_follow | if_like | if_retweet | comment_id |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
|  1 | 101 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:20 |  0 |  1 |   1 |       NULL |
|  2 | 102 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:15 |  0 |  0 |   1 |       NULL |
|  3 | 103 |     2001 | 2021-10-01 11:00:50 | 2021-10-01 11:01:15 |  0 |  1 |   0 |    1732526 |
|  4 | 102 |     2002 | 2021-09-10 11:00:00 | 2021-09-10 11:00:30 |  1 |  0 |   1 |       NULL |
|  5 | 103 |     2002 | 2021-10-01 10:59:05 | 2021-10-01 11:00:05 |  1 |  0 |   0 |       NULL |
+----+-----+----------+---------------------+---------------------+-+------------+------------+
5 rows in set (0.00 sec)

短视频信息表：tb_video_info（video_id：视频ID，author：创作者ID，tag：类别标签，duration：视频时长（秒）， release_time：发布时间），表中数据如下：

mysql> select * from tb_video_info;
+----+----------+--------+--------+----------+---------------------+
| id | video_id | author | tag    | duration | release_time        |
+----+----------+--------+--------+----------+---------------------+
|  1 |     2001 |    901 | 影视   |       30 | 2021-01-01 07:00:00 |
|  2 |     2002 |    901 | 美食   |       60 | 2021-01-01 07:00:00 |
|  3 |     2003 |    902 | 旅游   |       90 | 2020-01-01 07:00:00 |
+----+----------+--------+--------+----------+---------------------+
3 rows in set (0.00 sec)

【问题】统计在有用户互动的最近一个月（按包含当天在内的近 30 天算，比如 10 月 31 日的近 30 天为 10.2~10.31 之间的数据）中，每类视频的转发量和转发率（保留 3 位小数）。

说明：转发率＝转发量 ÷ 播放量。结果按转发率降序排序。查询结果如下：

tag retweet_cut retweet_rate
影视 2 0.667
美食 1 0.500

解答：

/*
select a.tag, a.retweet_cnt, round(a.retweet_cnt / b.cnt, 3) retweet_rate
from (select tv.tag, count(*) retweet_cntfrom tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_idwhere tu.start_time >= (select adddate(max(start_time), -30) tb_user_video_log)and if_retweet = 1group by tv.tag) a join(select tv.tag, count(*) cntfrom tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_idwhere tu.start_time >= (select adddate(max(start_time), -30) tb_user_video_log)group by tv.tag) bon a.tag = b.tag
order by retweet_rate desc;
*/
mysql> select a.tag, a.retweet_cnt, round(a.retweet_cnt / b.cnt, 3) retweet_rate-> from (select tv.tag, count(*) retweet_cnt->       from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id->       where tu.start_time >= (select adddate(max(start_time), -30) tb_user_video_log)->       and if_retweet = 1->       group by tv.tag) a join->       (select tv.tag, count(*) cnt->        from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id->        where tu.start_time >= (select adddate(max(start_time), -30) tb_user_video_log)->        group by tv.tag) b->        on a.tag = b.tag-> order by retweet_rate desc;
+--------+-------------+--------------+
| tag    | retweet_cnt | retweet_rate |
+--------+-------------+--------------+
| 影视   |           2 |        0.667 |
| 美食   |           1 |        0.500 |
+--------+-------------+--------------+
2 rows in set (0.00 sec)

171、分组统计（4）

该题目使用的表和数据如下：

/*
DROP TABLE IF EXISTS tb_user_video_log, tb_video_info;
CREATE TABLE tb_user_video_log (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',uid INT NOT NULL COMMENT '用户ID',video_id INT NOT NULL COMMENT '视频ID',start_time datetime COMMENT '开始观看时间',end_time datetime COMMENT '结束观看时间',if_follow TINYINT COMMENT '是否关注',if_like TINYINT COMMENT '是否点赞',if_retweet TINYINT COMMENT '是否转发',comment_id INT COMMENT '评论ID'
) CHARACTER SET utf8 COLLATE utf8_bin;CREATE TABLE tb_video_info (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',video_id INT UNIQUE NOT NULL COMMENT '视频ID',author INT NOT NULL COMMENT '创作者ID',tag VARCHAR(16) NOT NULL COMMENT '类别标签',duration INT NOT NULL COMMENT '视频时长(秒数)',release_time datetime NOT NULL COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_bin;INSERT INTO tb_user_video_log(uid, video_id, start_time, end_time, if_follow, if_like, if_retweet, comment_id) VALUES(101, 2001, '2021-09-01 10:00:00', '2021-09-01 10:00:20', 0, 1, 1, null),(105, 2002, '2021-09-10 11:00:00', '2021-09-10 11:00:30', 1, 0, 1, null),(101, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:20', 1, 1, 1, null),(102, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:15', 0, 0, 1, null),(103, 2001, '2021-10-01 11:00:50', '2021-10-01 11:01:15', 1, 1, 0, 1732526),(106, 2002, '2021-10-01 10:59:05', '2021-10-01 11:00:05', 2, 0, 0, null);INSERT INTO tb_video_info(video_id, author, tag, duration, release_time) VALUES(2001, 901, '影视', 30, '2021-01-01 7:00:00'),(2002, 901, '影视', 60, '2021-01-01 7:00:00'),(2003, 902, '旅游', 90, '2020-01-01 7:00:00'),(2004, 902, '美女', 90, '2020-01-01 8:00:00');*/

用户-视频互动表：tb_user_video_log（uid：用户ID, video_id：视频ID, start_time：开始观看时间，end_time：结束观看时间，if_follow：是否关注，if_like：是否点赞，if_retweet：是否转发，comment_id：评论ID），表中数据如下：

mysql> select * from tb_user_video_log;
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
| id | uid | video_id | start_time  | end_time  | if_follow | if_like | if_retweet | comment_id |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
|  1 | 101 |     2001 | 2021-09-01 10:00:00 | 2021-09-01 10:00:20 | 0 |  1 |   1 |       NULL |
|  2 | 105 |     2002 | 2021-09-10 11:00:00 | 2021-09-10 11:00:30 | 1 |  0 |   1 |       NULL |
|  3 | 101 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:20 | 1 |  1 |   1 |       NULL |
|  4 | 102 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:15 | 0 |  0 |   1 |       NULL |
|  5 | 103 |     2001 | 2021-10-01 11:00:50 | 2021-10-01 11:01:15 | 1 |  1 |   0 |    1732526 |
|  6 | 106 |     2002 | 2021-10-01 10:59:05 | 2021-10-01 11:00:05 | 2 |  0 |   0 |       NULL |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
6 rows in set (0.00 sec)

短视频信息表：tb_video_info（video_id：视频ID，author：创作者ID，tag：类别标签，duration：视频时长（秒）， release_time：发布时间），表中数据如下：

mysql> select * from tb_video_info;
+----+----------+--------+--------+----------+---------------------+
| id | video_id | author | tag    | duration | release_time        |
+----+----------+--------+--------+----------+---------------------+
|  1 |     2001 |    901 | 影视   |       30 | 2021-01-01 07:00:00 |
|  2 |     2002 |    901 | 影视   |       60 | 2021-01-01 07:00:00 |
|  3 |     2003 |    902 | 旅游   |       90 | 2020-01-01 07:00:00 |
|  4 |     2004 |    902 | 美女   |       90 | 2020-01-01 08:00:00 |
+----+----------+--------+--------+----------+---------------------+
4 rows in set (0.00 sec)

【问题】计算 2021 年里每个创作者每月的涨粉率及截止当月的总粉丝量。

说明：

（1）涨粉率=(加粉量 - 掉粉量) / 播放量。结果按创作者ID、总粉丝量升序排序。

（2）if_follow（是否关注）为 1 表示用户观看视频中关注了视频创作者，为 0 表示此次互动前后关注状态未发生变化，为 2 表示本次观看过程中取消了关注。

查询结果如下：

author month fans_growth_rate total_fans
901 2021-09 0.500 1
901 2021-10 0.250 2

结果：

/*
select a.author, a.month, round(a.fans_growth / b.cnt, 3) fans_growth_rate,(select @a := @a + a.fans_growth) total_fans
from (select tv.author, concat(left(start_time,4), '-', substr(start_time, 6,2)) month,sum(case if_follow when 1 then 1 when 0 then 0 when 2 then -1 end) fans_growthfrom tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_idgroup by tv.author, month) a join(select tv.author, concat(left(start_time,4), '-', substr(start_time, 6,2)) month,count(*) cntfrom tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_idgroup by tv.author, month) b on a.author = b.author and a.month = b.monthjoin (select @a := 0) c
order by a.author, total_fans;
*/
mysql> select a.author, a.month, ->        round(a.fans_growth / b.cnt, 3) fans_growth_rate,->        (select @a := @a + a.fans_growth) total_fans-> from (select tv.author, ->       concat(left(start_time,4), '-', substr(start_time, 6,2)) month,->       sum(case if_follow when 1 then 1 when 0 then 0 when 2 then -1 end) fans_growth->       from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id->       group by tv.author, month) a join->      (select tv.author, ->       concat(left(start_time,4), '-', substr(start_time, 6,2)) month,->       count(*) cnt->       from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id->       group by tv.author, month) b ->       on a.author = b.author and a.month = b.month->       join (select @a := 0) c-> order by a.author, total_fans;
+--------+---------+------------------+------------+
| author | month   | fans_growth_rate | total_fans |
+--------+---------+------------------+------------+
|    901 | 2021-09 |            0.500 |          1 |
|    901 | 2021-10 |            0.250 |          2 |
+--------+---------+------------------+------------+
2 rows in set (0.03 sec)

172、分组统计（5）

该题目使用的表和数据如下：

/*
DROP TABLE IF EXISTS tb_user_video_log, tb_video_info;
CREATE TABLE tb_user_video_log (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',uid INT NOT NULL COMMENT '用户ID',video_id INT NOT NULL COMMENT '视频ID',start_time datetime COMMENT '开始观看时间',end_time datetime COMMENT '结束观看时间',if_follow TINYINT COMMENT '是否关注',if_like TINYINT COMMENT '是否点赞',if_retweet TINYINT COMMENT '是否转发',comment_id INT COMMENT '评论ID'
) CHARACTER SET utf8 COLLATE utf8_bin;CREATE TABLE tb_video_info (id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',video_id INT UNIQUE NOT NULL COMMENT '视频ID',author INT NOT NULL COMMENT '创作者ID',tag VARCHAR(16) NOT NULL COMMENT '类别标签',duration INT NOT NULL COMMENT '视频时长(秒数)',release_time datetime NOT NULL COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_bin;INSERT INTO tb_user_video_log(uid, video_id, start_time, end_time, if_follow, if_like, if_retweet, comment_id) VALUES(101, 2001, '2021-09-24 10:00:00', '2021-09-24 10:00:20', 1, 1, 0, null),(105, 2002, '2021-09-25 11:00:00', '2021-09-25 11:00:30', 0, 0, 1, null),(102, 2002, '2021-09-25 11:00:00', '2021-09-25 11:00:30', 1, 1, 1, null),(101, 2002, '2021-09-26 11:00:00', '2021-09-26 11:00:30', 1, 0, 1, null),(101, 2002, '2021-09-27 11:00:00', '2021-09-27 11:00:30', 1, 1, 0, null),(102, 2002, '2021-09-28 11:00:00', '2021-09-28 11:00:30', 1, 0, 1, null),(103, 2002, '2021-09-29 11:00:00', '2021-09-29 11:00:30', 1, 0, 1, null),(102, 2002, '2021-09-30 11:00:00', '2021-09-30 11:00:30', 1, 1, 1, null),(101, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:20', 1, 1, 0, null),(102, 2001, '2021-10-01 10:00:00', '2021-10-01 10:00:15', 0, 0, 1, null),(103, 2001, '2021-10-01 11:00:50', '2021-10-01 11:01:15', 1, 1, 0, 1732526),(106, 2002, '2021-10-02 10:59:05', '2021-10-02 11:00:05', 2, 0, 1, null),(107, 2002, '2021-10-02 10:59:05', '2021-10-02 11:00:05', 1, 0, 1, null),(108, 2002, '2021-10-02 10:59:05', '2021-10-02 11:00:05', 1, 1, 1, null),(109, 2002, '2021-10-03 10:59:05', '2021-10-03 11:00:05', 0, 1, 0, null);INSERT INTO tb_video_info(video_id, author, tag, duration, release_time) VALUES(2001, 901, '旅游', 30, '2020-01-01 7:00:00'),(2002, 901, '旅游', 60, '2021-01-01 7:00:00'),(2003, 902, '影视', 90, '2020-01-01 7:00:00'),(2004, 902, '美女', 90, '2020-01-01 8:00:00');*/

用户-视频互动表：tb_user_video_log（uid：用户ID, video_id：视频ID, start_time：开始观看时间，end_time：结束观看时间，if_follow：是否关注，if_like：是否点赞，if_retweet：是否转发，comment_id：评论ID），表中数据如下：

mysql> select * from tb_user_video_log;
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
| id | uid | video_id | start_time | end_time   | if_follow | if_like | if_retweet | comment_id |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
|  1 | 101 |     2001 | 2021-09-24 10:00:00 | 2021-09-24 10:00:20 | 1 |  1 |  0 |       NULL |
|  2 | 105 |     2002 | 2021-09-25 11:00:00 | 2021-09-25 11:00:30 | 0 |  0 |  1 |       NULL |
|  3 | 102 |     2002 | 2021-09-25 11:00:00 | 2021-09-25 11:00:30 | 1 |  1 |  1 |       NULL |
|  4 | 101 |     2002 | 2021-09-26 11:00:00 | 2021-09-26 11:00:30 | 1 |  0 |  1 |       NULL |
|  5 | 101 |     2002 | 2021-09-27 11:00:00 | 2021-09-27 11:00:30 | 1 |  1 |  0 |       NULL |
|  6 | 102 |     2002 | 2021-09-28 11:00:00 | 2021-09-28 11:00:30 | 1 |  0 |  1 |       NULL |
|  7 | 103 |     2002 | 2021-09-29 11:00:00 | 2021-09-29 11:00:30 | 1 |  0 |  1 |       NULL |
|  8 | 102 |     2002 | 2021-09-30 11:00:00 | 2021-09-30 11:00:30 | 1 |  1 |  1 |       NULL |
|  9 | 101 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:20 | 1 |  1 |  0 |       NULL |
| 10 | 102 |     2001 | 2021-10-01 10:00:00 | 2021-10-01 10:00:15 | 0 |  0 |  1 |       NULL |
| 11 | 103 |     2001 | 2021-10-01 11:00:50 | 2021-10-01 11:01:15 | 1 |  1 |  0 |    1732526 |
| 12 | 106 |     2002 | 2021-10-02 10:59:05 | 2021-10-02 11:00:05 | 2 |  0 |  1 |       NULL |
| 13 | 107 |     2002 | 2021-10-02 10:59:05 | 2021-10-02 11:00:05 | 1 |  0 |  1 |       NULL |
| 14 | 108 |     2002 | 2021-10-02 10:59:05 | 2021-10-02 11:00:05 | 1 |  1 |  1 |       NULL |
| 15 | 109 |     2002 | 2021-10-03 10:59:05 | 2021-10-03 11:00:05 | 0 |  1 |  0 |       NULL |
+----+-----+----------+---------------------+---------------------+-----------+---------+--------+
15 rows in set (0.00 sec)

短视频信息表：tb_video_info（video_id：视频ID，author：创作者ID，tag：类别标签，duration：视频时长（秒）， release_time：发布时间），表中数据如下：

mysql> select * from tb_video_info;
+----+----------+--------+--------+----------+---------------------+
| id | video_id | author | tag    | duration | release_time        |
+----+----------+--------+--------+----------+---------------------+
|  1 |     2001 |    901 | 旅游   |       30 | 2020-01-01 07:00:00 |
|  2 |     2002 |    901 | 旅游   |       60 | 2021-01-01 07:00:00 |
|  3 |     2003 |    902 | 影视   |       90 | 2020-01-01 07:00:00 |
|  4 |     2004 |    902 | 美女   |       90 | 2020-01-01 08:00:00 |
+----+----------+--------+--------+----------+---------------------+
4 rows in set (0.00 sec)

【问题】统计 2021 年国庆头 3 天每类视频每天的近一周总点赞量和一周内最大单天转发量，结果按视频类别降序、日期升序排序。假设数据库中数据足够多，至少每个类别下国庆头 3 天及之前一周的每天都有播放记录。查询结果如下：

tag dt sum_like_cnt_7d max_retweet_cnt_7d
旅游 2021-10-01 5 2
旅游 2021-10-02 5 3
旅游 2021-10-03 6 3

解答：

/*
select tv.tag, date(tu.start_time) dt,(select sum(if_like) from tb_user_video_log where date(start_time) between adddate(dt, -6) and dtand video_id in (select video_id from tb_video_info where tag = tv.tag)) sum_like_cnt_7d,       (select sum(if_retweet) aa from tb_user_video_log where date(start_time) between adddate(dt, -6) and dtand video_id in (select video_id from tb_video_info where tag = tv.tag)group by date(start_time) order by aa desc limit 1             ) max_retweet_cnt_7d
from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id
where tu.start_time between '2021-10-01 00:00:00' and '2021-10-03 23:59:59'
group by tv.tag, dt
order by tv.tag desc, dt;
*/
mysql> select tv.tag, date(tu.start_time) dt,->        (select sum(if_like) from tb_user_video_log ->         where date(start_time) between adddate(dt, -6) and dt->               and video_id in (select video_id from tb_video_info where tag = tv.tag)->        ) sum_like_cnt_7d,       ->        (select sum(if_retweet) aa ->         from tb_user_video_log ->         where date(start_time) between adddate(dt, -6) and dt->         and video_id in (select video_id from tb_video_info where tag = tv.tag)->         group by date(start_time) ->         order by aa desc limit 1             ->         ) max_retweet_cnt_7d-> from tb_user_video_log tu join tb_video_info tv on tu.video_id = tv.video_id-> where tu.start_time between '2021-10-01 00:00:00' and '2021-10-03 23:59:59'-> group by tv.tag, dt-> order by tv.tag desc, dt;
+--------+------------+-----------------+--------------------+
| tag    | dt         | sum_like_cnt_7d | max_retweet_cnt_7d |
+--------+------------+-----------------+--------------------+
| 旅游   | 2021-10-01 |               5 |                  2 |
| 旅游   | 2021-10-02 |               5 |                  3 |
| 旅游   | 2021-10-03 |               6 |                  3 |
+--------+------------+-----------------+--------------------+
3 rows in set (0.00 sec)

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