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哈喽！大家好，我是【IT邦德】，江湖人称jeames007，10年DBA工作经验
中国DBA联盟(ACDU)成员，目前从事DBA及程序编程😜😜😜
擅长Oracle、MySQL、PG 运维开发，备份恢复，安装迁移，性能优化、故障应急处理。
❤️❤️❤️感谢各位大可爱小可爱！❤️❤️❤️
前言
SQL每个人都要用，但是用来衡量产出的并不是SQL本身，你需要用这个工具，去创造其它的价值。🐴 SQL180 某宝店铺的SPU数量
🚀 建表语句
drop table if exists course_tb;
CREATE TABLE course_tb(
course_id int(10) NOT NULL,
course_name char(10) NOT NULL,
course_datetime char(30) NOT NULL);
INSERT INTO course_tb VALUES(1, 'Python', '2021-12-1 19:00-21:00');
INSERT INTO course_tb VALUES(2, 'SQL', '2021-12-2 19:00-21:00');
INSERT INTO course_tb VALUES(3, 'R', '2021-12-3 19:00-21:00');
drop table if exists behavior_tb;
CREATE TABLE behavior_tb(
user_id int(10) NOT NULL,
if_vw int(10) NOT NULL,
if_fav int(10) NOT NULL,
if_sign int(10) NOT NULL,
course_id int(10) NOT NULL);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 3);
INSERT INTO behavior_tb VALUES(101, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(101, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(101, 1, 0, 0, 3);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 3);
INSERT INTO behavior_tb VALUES(103, 1, 1, 0, 1);
INSERT INTO behavior_tb VALUES(103, 1, 0, 0, 2);
INSERT INTO behavior_tb VALUES(103, 1, 0, 0, 3);
INSERT INTO behavior_tb VALUES(104, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(104, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(104, 1, 1, 0, 3);
INSERT INTO behavior_tb VALUES(105, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(106, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(107, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(107, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(108, 1, 1, 1, 3);
📖 需求
请你统计每个科目的转换率（sign_rate(%)，转化率=报名人数/浏览人数，结果保留两位小数）。
注：按照course_id升序排序。
🍌🍌 答案
select a.course_id,
b.course_name,
round(sum(if_sign)/sum(if_vw)*100,2) `sign_rate(%)`
from behavior_tb a
left join course_tb b
on a.course_id = b.course_id
group by a.course_id , b.course_name
order by a.course_id
🐴 SQL186 牛客直播开始时各直播间在线人数
🚀 建表语句
CREATE TABLE course_tb(
course_id int(10) NOT NULL,
course_name char(10) NOT NULL,
course_datetime char(30) NOT NULL);
INSERT INTO course_tb VALUES(1, 'Python', '2021-12-1 19:00-21:00');
INSERT INTO course_tb VALUES(2, 'SQL', '2021-12-2 19:00-21:00');
INSERT INTO course_tb VALUES(3, 'R', '2021-12-3 19:00-21:00');
CREATE TABLE attend_tb(
user_id int(10) NOT NULL,
course_id int(10) NOT NULL,
in_datetime datetime NOT NULL,
out_datetime datetime NOT NULL
);
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:00:00', '2021-12-1 19:28:00');
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:30:00', '2021-12-1 19:53:00');
INSERT INTO attend_tb VALUES(101, 1, '2021-12-1 19:00:00', '2021-12-1 20:55:00');
INSERT INTO attend_tb VALUES(102, 1, '2021-12-1 19:00:00', '2021-12-1 19:05:00');
INSERT INTO attend_tb VALUES(104, 1, '2021-12-1 19:00:00', '2021-12-1 20:59:00');
INSERT INTO attend_tb VALUES(101, 2, '2021-12-2 19:05:00', '2021-12-2 20:58:00');
INSERT INTO attend_tb VALUES(102, 2, '2021-12-2 18:55:00', '2021-12-2 21:00:00');
INSERT INTO attend_tb VALUES(104, 2, '2021-12-2 18:57:00', '2021-12-2 20:56:00');
INSERT INTO attend_tb VALUES(107, 2, '2021-12-2 19:10:00', '2021-12-2 19:18:00');
INSERT INTO attend_tb VALUES(100, 3, '2021-12-3 19:01:00', '2021-12-3 21:00:00');
INSERT INTO attend_tb VALUES(102, 3, '2021-12-3 18:58:00', '2021-12-3 19:05:00');
INSERT INTO attend_tb VALUES(108, 3, '2021-12-3 19:01:00', '2021-12-3 19:56:00');
📖 需求
请你统计直播开始时（19：00），各科目的在线人数，以上例子的输出结果为（按照course_id升序排序）
🍌🍌 答案
select
c.course_id,
c.course_name,
count(distinct user_id) asonline_num
from course_tb c
join attend_tb a using (course_id)
where time(in_datetime)<='19:00:00'
and time(out_datetime)>='19:00:00'
group by c.course_id,c.course_name
order by c.course_id
🐴 SQL187 牛客直播各科目平均观看时长
drop table if exists course_tb;
CREATE TABLE course_tb(
course_id int(10) NOT NULL,
course_name char(10) NOT NULL,
course_datetime char(30) NOT NULL);
INSERT INTO course_tb VALUES(1, 'Python', '2021-12-1 19:00-21:00');
INSERT INTO course_tb VALUES(2, 'SQL', '2021-12-2 19:00-21:00');
INSERT INTO course_tb VALUES(3, 'R', '2021-12-3 19:00-21:00');
drop table if exists attend_tb;
CREATE TABLE attend_tb(
user_id int(10) NOT NULL,
course_id int(10) NOT NULL,
in_datetime datetime NOT NULL,
out_datetime datetime NOT NULL
);
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:00:00', '2021-12-1 19:28:00');
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:30:00', '2021-12-1 19:53:00');
INSERT INTO attend_tb VALUES(101, 1, '2021-12-1 19:00:00', '2021-12-1 20:55:00');
INSERT INTO attend_tb VALUES(102, 1, '2021-12-1 19:00:00', '2021-12-1 19:05:00');
INSERT INTO attend_tb VALUES(104, 1, '2021-12-1 19:00:00', '2021-12-1 20:59:00');
INSERT INTO attend_tb VALUES(101, 2, '2021-12-2 19:05:00', '2021-12-2 20:58:00');
INSERT INTO attend_tb VALUES(102, 2, '2021-12-2 18:55:00', '2021-12-2 21:00:00');
INSERT INTO attend_tb VALUES(104, 2, '2021-12-2 18:57:00', '2021-12-2 20:56:00');
INSERT INTO attend_tb VALUES(107, 2, '2021-12-2 19:10:00', '2021-12-2 19:18:00');
INSERT INTO attend_tb VALUES(100, 3, '2021-12-3 19:01:00', '2021-12-3 21:00:00');
INSERT INTO attend_tb VALUES(102, 3, '2021-12-3 18:58:00', '2021-12-3 19:05:00');
INSERT INTO attend_tb VALUES(108, 3, '2021-12-3 19:01:00', '2021-12-3 19:56:00');
📖 需求
请你统计每个科目的平均观看时长（观看时长定义为离开直播间的时间与进入直播间的时间之差，单位是分钟），
输出结果按平均观看时长降序排序，结果保留两位小数。
'🍌🍌 答案
select c.course_name,
round(avg(TIMESTAMPDIFF(minute,a.in_datetime,a.out_datetime)),2) avg_len
from course_tb c left join attend_tb a using(course_id)
group by c.course_name
order by avg_len desc
🐴 SQL188 牛客直播各科目出勤率
🚀 建表语句
drop table if exists course_tb;
CREATE TABLE course_tb(
course_id int(10) NOT NULL,
course_name char(10) NOT NULL,
course_datetime char(30) NOT NULL);
INSERT INTO course_tb VALUES(1, 'Python', '2021-12-1 19:00-21:00');
INSERT INTO course_tb VALUES(2, 'SQL', '2021-12-2 19:00-21:00');
INSERT INTO course_tb VALUES(3, 'R', '2021-12-3 19:00-21:00');
drop table if exists behavior_tb;
CREATE TABLE behavior_tb(
user_id int(10) NOT NULL,
if_vw int(10) NOT NULL,
if_fav int(10) NOT NULL,
if_sign int(10) NOT NULL,
course_id int(10) NOT NULL);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(100, 1, 1, 1, 3);
INSERT INTO behavior_tb VALUES(101, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(101, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(101, 1, 0, 0, 3);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(102, 1, 1, 1, 3);
INSERT INTO behavior_tb VALUES(103, 1, 1, 0, 1);
INSERT INTO behavior_tb VALUES(103, 1, 0, 0, 2);
INSERT INTO behavior_tb VALUES(103, 1, 0, 0, 3);
INSERT INTO behavior_tb VALUES(104, 1, 1, 1, 1);
INSERT INTO behavior_tb VALUES(104, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(104, 1, 1, 0, 3);
INSERT INTO behavior_tb VALUES(105, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(106, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(107, 1, 0, 0, 1);
INSERT INTO behavior_tb VALUES(107, 1, 1, 1, 2);
INSERT INTO behavior_tb VALUES(108, 1, 1, 1, 3);
drop table if exists attend_tb;
CREATE TABLE attend_tb(
user_id int(10) NOT NULL,
course_id int(10) NOT NULL,
in_datetime datetime NOT NULL,
out_datetime datetime NOT NULL
);
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:00:00', '2021-12-1 19:28:00');
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:30:00', '2021-12-1 19:53:00');
INSERT INTO attend_tb VALUES(101, 1, '2021-12-1 19:00:00', '2021-12-1 20:55:00');
INSERT INTO attend_tb VALUES(102, 1, '2021-12-1 19:00:00', '2021-12-1 19:05:00');
INSERT INTO attend_tb VALUES(104, 1, '2021-12-1 19:00:00', '2021-12-1 20:59:00');
INSERT INTO attend_tb VALUES(101, 2, '2021-12-2 19:05:00', '2021-12-2 20:58:00');
INSERT INTO attend_tb VALUES(102, 2, '2021-12-2 18:55:00', '2021-12-2 21:00:00');
INSERT INTO attend_tb VALUES(104, 2, '2021-12-2 18:57:00', '2021-12-2 20:56:00');
INSERT INTO attend_tb VALUES(107, 2, '2021-12-2 19:10:00', '2021-12-2 19:18:00');
INSERT INTO attend_tb VALUES(100, 3, '2021-12-3 19:01:00', '2021-12-3 21:00:00');
INSERT INTO attend_tb VALUES(102, 3, '2021-12-3 18:58:00', '2021-12-3 19:05:00');
INSERT INTO attend_tb VALUES(108, 3, '2021-12-3 19:01:00', '2021-12-3 19:56:00');
📖 需求
请你统计每个科目的出勤率（attend_rate(%)，结果保留两位小数），
出勤率=出勤（在线时长10分钟及以上）人数 / 报名人数，输出结果按course_id升序排序，以上数据的输出结果如下：
'🍌🍌 答案
select c.course_id, course_name,
round(count(distinct if(TIMESTAMPDIFF(second,in_datetime,out_datetime) >= 600, a.user_id, null))/ count(distinct if(if_sign=1,b.user_id,null))*100,2)
from attend_tb a right join behavior_tb b
on a.user_id = b.user_id and a.course_id = b.course_id
join course_tb c
on b.course_id = c.course_id
group by c.course_id, course_name
order by c.course_id
🐴 SQL189 牛客直播各科目同时在线人数
🚀 建表语句
drop table if exists course_tb;
CREATE TABLE course_tb(
course_id int(10) NOT NULL,
course_name char(10) NOT NULL,
course_datetime char(30) NOT NULL);
INSERT INTO course_tb VALUES(1, 'Python', '2021-12-1 19:00-21:00');
INSERT INTO course_tb VALUES(2, 'SQL', '2021-12-2 19:00-21:00');
INSERT INTO course_tb VALUES(3, 'R', '2021-12-3 19:00-21:00');
drop table if exists attend_tb;
CREATE TABLE attend_tb(
user_id int(10) NOT NULL,
course_id int(10) NOT NULL,
in_datetime datetime NOT NULL,
out_datetime datetime NOT NULL
);
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:00:00', '2021-12-1 19:28:00');
INSERT INTO attend_tb VALUES(100, 1, '2021-12-1 19:30:00', '2021-12-1 19:53:00');
INSERT INTO attend_tb VALUES(101, 1, '2021-12-1 19:00:00', '2021-12-1 20:55:00');
INSERT INTO attend_tb VALUES(102, 1, '2021-12-1 19:00:00', '2021-12-1 19:05:00');
INSERT INTO attend_tb VALUES(104, 1, '2021-12-1 19:00:00', '2021-12-1 20:59:00');
INSERT INTO attend_tb VALUES(101, 2, '2021-12-2 19:05:00', '2021-12-2 20:58:00');
INSERT INTO attend_tb VALUES(102, 2, '2021-12-2 18:55:00', '2021-12-2 21:00:00');
INSERT INTO attend_tb VALUES(104, 2, '2021-12-2 18:57:00', '2021-12-2 20:56:00');
INSERT INTO attend_tb VALUES(107, 2, '2021-12-2 19:10:00', '2021-12-2 19:18:00');
INSERT INTO attend_tb VALUES(100, 3, '2021-12-3 19:01:00', '2021-12-3 21:00:00');
INSERT INTO attend_tb VALUES(102, 3, '2021-12-3 18:58:00', '2021-12-3 19:05:00');
INSERT INTO attend_tb VALUES(108, 3, '2021-12-3 19:01:00', '2021-12-3 19:56:00');
📖 需求
请你统计每个科目最大同时在线人数（按course_id排序）
🍌🍌 答案
select ct.course_id,ct.course_name,bt.max_num
from course_tb ct
join(
select course_id,max(at_num) as max_num
from(
select*, sum(num)over(partition by course_id order by course_id,at_time) as at_num
from(
select user_id,course_id,time(in_datetime) as at_time, 1 num
from attend_tb
union all
select user_id,course_id,time(out_datetime) as at_time, -1 num
from attend_tb
order by course_id,at_time
) a
) b
group by course_id
) bt
on ct.course_id=bt.course_id
