SQL练习题三十一-每季十题(十)

350. 连续登陆大于等于7天的用户,及连续登陆的开始,结束时间

create table my_data.log_user_login(
    user_name varchar(10),
    time_login DATETIME
);

insert into log_user_login value('aaa','2022-06-01 11:30:45');
insert into log_user_login value('aaa','2022-06-01 12:30:45');
insert into log_user_login value('aaa','2022-06-02 11:30:45');
insert into log_user_login value('aaa','2022-06-03 11:30:45');

insert into log_user_login value('aaa','2022-06-06 11:30:45');
insert into log_user_login value('aaa','2022-06-07 11:30:45');
insert into log_user_login value('aaa','2022-06-07 17:30:45');
insert into log_user_login value('aaa','2022-06-08 11:30:45');
insert into log_user_login value('aaa','2022-06-08 19:30:45');
insert into log_user_login value('aaa','2022-06-09 11:30:45');
insert into log_user_login value('aaa','2022-06-10 11:30:45');
insert into log_user_login value('aaa','2022-06-11 11:30:45');
insert into log_user_login value('aaa','2022-06-12 11:30:45');

insert into log_user_login value('bbb','2022-06-02 11:30:45');
insert into log_user_login value('bbb','2022-06-03 11:30:45');
insert into log_user_login value('bbb','2022-06-04 11:30:45');
insert into log_user_login value('bbb','2022-06-05 11:30:45');
insert into log_user_login value('bbb','2022-06-06 11:30:45');
insert into log_user_login value('bbb','2022-06-07 11:30:45');
insert into log_user_login value('bbb','2022-06-08 11:30:45');
insert into log_user_login value('bbb','2022-06-09 11:30:45');
insert into log_user_login value('bbb','2022-06-29 11:30:45');

非常经典的题目,有重复数据先去重,然后row_number()开窗解决

MySQL DATE_SUB() 函数

select user_name,min(time_login) as start_time_login ,max(time_login) as end_time_login ,count(1) as login_day_cnt
from (
         select user_name, time_login, date_sub(time_login, INTERVAL rn DAY) as tag
         from (
                  select user_name,
                         time_login,
                         row_number() over (partition by user_name order by time_login) as rn
                  from (
                           select user_name, cast(time_login as date) as time_login
                           from log_user_login
                           group by user_name, cast(time_login as date)
                       ) t1
              ) t2
     ) t3
group by  user_name,tag
having count(1) >= 7 ;

351. 连续点击大于等于三次的用户数,中间不能有别人的点击

create table my_data.log_user_click_tf(
    user_name varchar(10),
    time_login DATETIME
);
insert into log_user_click_tf value('aaa','2022-06-01 11:30:45');
insert into log_user_click_tf value('aaa','2022-06-01 12:30:45');
insert into log_user_click_tf value('bbb','2022-06-01 13:30:45');
insert into log_user_click_tf value('aaa','2022-06-01 14:30:45');
insert into log_user_click_tf value('aaa','2022-06-01 15:30:45');
insert into log_user_click_tf value('ccc','2022-06-01 16:30:45');
insert into log_user_click_tf value('ccc','2022-06-01 18:30:45');
insert into log_user_click_tf value('ccc','2022-06-01 19:30:45');
insert into log_user_click_tf value('ccc','2022-06-01 20:30:45');
insert into log_user_click_tf value('ddd','2022-06-01 21:30:45');
insert into log_user_click_tf value('ddd','2022-06-01 22:30:45');
insert into log_user_click_tf value('ddd','2022-06-01 23:30:45');

偏移量函数的使用

select count(distinct user_name) as dis_cnt_user
from (
         select user_name,
                lag(user_name, 1) over (order by time_login) as before_1_user_name,
                lag(user_name, 2) over (order by time_login) as before_2_user_name
         from log_user_click_tf
     ) t1 where user_name = before_1_user_name and user_name = before_2_user_name

分组的使用

select
count(distinct user_name) as dis_cnt_user
from (
         select user_name
         from (
                  select user_name,
                         tag - group_tag as rn
                  from (
                           select user_name,
                                  row_number() over (partition by user_name order by time_login) as group_tag,
                                  row_number() over (order by time_login)                        as tag
                           from log_user_click_tf
                       ) t1
              ) t2
         group by user_name, rn
         having count(1) >= 3
     ) t3

352. 计算除去部门最高工资和最低工资的平均工资

create table deptno_salary_hr(
    user_name varchar(10),
    deptno int,
    salart double
);
insert into deptno_salary_hr value('a',1,10000);
insert into deptno_salary_hr value('b',1,20000);
insert into deptno_salary_hr value('c',1,30000);
insert into deptno_salary_hr value('d',1,40000);
insert into deptno_salary_hr value('e',1,50000);
insert into deptno_salary_hr value('f',1,60000);
insert into deptno_salary_hr value('a1',2,10000);
insert into deptno_salary_hr value('b1',2,10000);
insert into deptno_salary_hr value('c1',2,30000);
insert into deptno_salary_hr value('d1',2,40000);

正排和倒排的使用,求中位数也能用

select sum(salart) * 1.0 / count(1) as avg_salary
from (
         select deptno,
                salart,
                dense_rank() over (partition by deptno order by salart)       as asc_rn,
                dense_rank() over (partition by deptno order by salart desc ) as desc_rn
         from deptno_salary_hr
     ) t1
where asc_rn > 1 and desc_rn > 1
group by deptno

353. 留存率

格式

自联结的应用,有没有更好的思路???


create  table log_user_view_retained_df(
      user_name varchar(10),
      time_login DATETIME
);


insert into log_user_view_retained_df value('a0','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a2','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a3','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a4','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a5','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a6','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a7','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a8','2022-06-01 23:30:45');
insert into log_user_view_retained_df value('a9','2022-06-01 23:30:45');

insert into log_user_view_retained_df value('a0','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a2','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a3','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a4','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a5','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a6','2022-06-02 23:30:45');
insert into log_user_view_retained_df value('a7','2022-06-02 23:30:45');

insert into log_user_view_retained_df value('a0','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a2','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a3','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a4','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a5','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a6','2022-06-03 23:30:45');
insert into log_user_view_retained_df value('a7','2022-06-03 23:30:45');

insert into log_user_view_retained_df value('a0','2022-06-04 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-04 23:30:45');

insert into log_user_view_retained_df value('a0','2022-06-05 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-05 23:30:45');

insert into log_user_view_retained_df value('a0','2022-06-06 23:30:45');
insert into log_user_view_retained_df value('a1','2022-06-06 23:30:45');

insert into log_user_view_retained_df value('a1','2022-06-07 23:30:45');

select
time_login,
count(distinct user_name) as '活跃用户',
count(distinct case when interval_login =1 then user_name else null end ) as '次日留存用户',
count(distinct case when interval_login =1 then user_name else null end ) / count(distinct user_name) as '次日留存率',
count(distinct case when interval_login =3 then user_name else null end ) as '三日留存用户',
count(distinct case when interval_login =3 then user_name else null end ) / count(distinct user_name) as '三日留存率'
from (
         select t1.user_name,
                cast(t1.time_login as date) as time_login,
                datediff(cast(t2.time_login as date), cast(t1.time_login as date)) as interval_login
         from log_user_view_retained_df t1
                  join log_user_view_retained_df t2
                       on cast(t1.time_login as date) >= '2022-06-01' and cast(t1.time_login as date) <= '2022-06-30'
                           and cast(t2.time_login as date) >= '2022-06-01' and
                          cast(t2.time_login as date) <= '2022-06-30'
                           and t1.user_name = t2.user_name
     ) t3
group by time_login

354. 流失回归率

分析统计6.1日活跃玩家的流失率回归率,公式:流失3日回归率 6/2-6/3未登陆但是6/4日登陆的玩家 / 6/2-6/3未登陆的玩家总数

with interval_cnt as (select count(1) as cnt from log_user_view_retained_df where cast(time_login as date)  = '2022-07-01'),
interval_user as (
select user_name from log_user_view_retained_df where cast(time_login as date)  = '2022-07-01'
    )
select start_login_time,user_cnt,user_cnt * 1.0 / if( cnt - sum(user_cnt) over (order by start_login_time rows  between  unbounded preceding and 1 preceding) is null ,0,cnt - sum(user_cnt) over (order by start_login_time rows  between  unbounded preceding and 1 preceding))
from (
select cast(start_login_timestamp as date) as  start_login_time,count(1) as user_cnt,cnt
from (
    # 取用户在区间最早的登录时间
         select t1.user_name, min(t1.time_login) as start_login_timestamp,cnt
         from log_user_view_retained_df t1
                  join interval_user t2
                       on t1.user_name = t2.user_name
                           and cast(t1.time_login as date) >  '2022-07-01' and
                          cast(t1.time_login as date) <= '2022-07-30'
                   join interval_cnt  tmp_cnt
         group by t1.user_name,cnt
     ) t3
group by cast(start_login_timestamp as date),cnt ) t4;

355. AB球队得分流水表,得到连续三次得分的队员名字和每次赶超对手的球员名字

连续三次得分的队员名字:和连续点击大于等于三次的用户数,中间不能有别人的点击这题是一个思路

select  team,name
from (
         select team,
                name,
                lag(name, 1) over (partition by team order by score_time) as before_1_team_name,
                lag(name, 2) over (partition by team order by score_time) as before_2_team_name
         from team_score_detail
     ) t1
where name = before_1_team_name and name=before_2_team_name
group by team,name

思路二:两两分组,打标签

select team, name
from (
         select team, name, if(lag(name, 1) over (partition by team order by score_time) = name, 1, 0) as tag
         from team_score_detail
     ) t1
where  tag = 1
group by team,name,tag
having count(1) >= 3
# 也可以if判断中打标签换过来,然后开窗累计,不用过滤tag=1这种方式

每次赶超对手的球员名字,case when的使用

select team,
       name,
       A_sum_score ,
       B_sum_score
from (
         select team,
                name,
                A_sum_score ,
                B_sum_score,
                A_sum_score - B_sum_score                                    as c_score,
                lag(A_sum_score - B_sum_score, 1) over (order by score_time) as before_c_score
         from (
                  select team,
                         name,
                         score_time,
                         sum(A_score) over (order by score_time)  as A_sum_score,
                         sum(B_score) over ( order by score_time) as B_sum_score
                  from (
                           select team,
                                  name,
                                  score_time,
                                  case when team = 'A' then score else 0 end as A_score,
                                  case when team = 'B' then score else 0 end as B_score
                           from team_score_detail
                       ) t1
              ) t2
     ) t3 where c_score * before_c_score < 0
# c_score * before_c_score < 0说明就是反超

第一次不算,算的话,case when 判断一下,不用c_score * before_c_score < 0

case when diff_score > 0 and lag(diff_score) over (order by score_time asc) < 0 then 1
              when diff_score < 0 and lag(diff_score) over (order by score_time asc) > 0 then 1
              when diff_score is not null and lag(diff_score) over (order by score_time asc) is null then 1
              else 0
         end

356. 拉链表

数据仓库建模的一个体现,非常经典啊,我的经验是只要是一个维度的分析(参与时间),基本都能用拉链表,多个维度分析,万物皆可bitmap,哈哈哈

create table user_act_range(
first_dt    date,
guid        varchar(10),
range_start date,
range_end   date
);
# 初始化
insert into user_act_range value('2020-01-01','X0001','2020-01-01','2022-01-01');
insert into user_act_range value('2020-01-01','X0001','2020-03-01','9999-12-31');
insert into user_act_range value('2020-06-01','X0002','2022-06-01','9999-12-31');
insert into user_act_range value('2020-01-01','X0003','2020-01-01','2022-01-01');


# 用户登陆表(就是今天有哪些用户登陆了)
create table user_session_login(
     guid  varchar(10),
     login date
);
insert into user_session_login value('X0002','2022-06-26');
insert into user_session_login value('X0003','2022-06-26');
insert into user_session_login value('X0004','2022-06-26');

两部分,第一部分今天登陆了,至少昨天没有登陆的用户单独union all,第二部分两张表full join 分类讨论,封闭区间,9999-12-31,新用户的情况

357. 认识的组合数

快手面试题,非常经典的题目,再写一遍

需求:现有城市网吧访问数据，字段：网吧id，访客id（身份证号），上线时间，下线时间
规则1、如果有两个用户在一家网吧的前后上下线时间在10分钟以内，则两人可能认识
规则2、如果这两个用户在三家以上网吧出现【规则1】的情况，则两人一定认识
需求：
该城市上网用户中两人一定认识的组合数

自联结的应用

设表名：table0
字段：wid ， uid ，ontime ，offtime
select
    id,
    count(distinct wid) c
from
    (select
        wid,
        concat(t0.uid,t1.uid) as id
    from
        (select
            wid,
            uid,
            unix_timestamp(ontime,'yyyyMMdd HH:mm:ss') as ontime,
            unix_timestamp(offtime,'yyyyMMdd HH:mm:ss') as offtime
        from 
            table0
        )t0
    join
        (select
            wid,
            uid,
            unix_timestamp(ontime,'yyyyMMdd HH:mm:ss') as ontime,
            unix_timestamp(offtime,'yyyyMMdd HH:mm:ss') as offtime
        from 
            table0
        )t1
    on t0.wid=t1.wid
        and t0.uid>t1.uid
        and (abs(t0.ontime-t1.ontime)<10*60 or abs(t0.offtime-t1.offtime)<10*60)
        
    )t0
group by 
    id
having
    c>=3

思路是对的,没测试...

select count(uid) as com_cnt
from(
    select uid,pre_uid
          ,count(distinct wid) as flag
    from(
        select wid
              ,uid
              ,abs(unix_timestamp(ontime,'yyyy-MM-dd HH:mm:ss')-unix_timestamp(lag(ontime,1,'1970-01-01 08:00:00') over(partition by wid order by ontime),'yyyy-MM-dd HH:mm:ss')) / 60 ontime_diff
              ,abs(unix_timestamp(offtime,'yyyy-MM-dd HH:mm:ss')-unix_timestamp(lag(offtime,1,'1970-01-01 08:00:00') over(partition by wid order by offtime),'yyyy-MM-dd HH:mm:ss')) / 60 offtime_diff
              ,lag(uid) over (partition by wid order by offtime) as pre_uid
        from table0
    ) m
    where  (ontime_diff<=10 or offtime_diff<=10)
    group by uid,pre_uid
) n
where flag>=3

358. 中位数

面试题,非常经典的题目

表中保存了数字的值以及其个数,求取中位数,在此表中,数字为0,0,0,0,0,0,0,1,2,2,2.3,所以中位数为(0+0)/2

create  table if not exists c0629(
 Number int,Frequency INT
);
insert into  c0629 values (0,7),(1,1),(2,3),(3,1);

请编写一个查询来查找所有数字的中位数并将结果命名为 median 。注意：什么是中位数？当一串数字是奇数个时，例如8,3,5,1,4。我们按顺序排列后为：1,3,4,5,8。那么4就是中位数
当一串数字为偶数个时，例如8,3,5,1,4,2。我们按顺序排列后为：1,2,3,4,5,8。那么(3+4)/2=3.5就是中位数。

从位置上理解中位数,正序逆序的应用

select avg(number) as median
from
(select Number, frequency,
        sum(frequency) over(order by number asc) as total,
        sum(frequency) over(order by number desc) as total1
from c0629
order by number asc)as a
where total>=(select sum(frequency) from c0629)/2
and total1>=(select sum(frequency) from c0629)/2

看一下这种写法...我已经看不懂了..测试了一下....参考自连接比较法,第一步其实求取的比多少大,比多少小的问题
这里的中位数定义是,比中位数大的数 - 比中位数下的数的绝对值是最小的(前提是没有重复值),有重复值的情况下,选出equal大于或等于margin绝对值的num,为什么要这么做,如果(不大于或等于),那么就一定不是中位数呀
SQL笔面试题：如何求取中位数？

select
 Number,   (select sum(Frequency) from c0629 where Number <= n.Number), (select sum(Frequency) from c0629 where Number >= n.Number)
from
    c0629 as n

select
    avg(n.Number) as median
from
    c0629 as n
where
    n.Frequency >= abs(
        (select sum(Frequency) from c0629 where Number <= n.Number) -
        (select sum(Frequency) from c0629 where Number >= n.Number)
    );

359. 混合排序

非常经典

示例

name 是店铺名称，名称中带有“-”表示分店，score 是销售额。出题人希望能依据城市、销售额查看各个店铺的销售数据，并且当存在分店时，分店能紧挨在总店后面按照 id 排序

create table order_data (
     id int ,
     city varchar(1),
     name  varchar(4),
     score int
);

insert into order_data values (1,'a','A',100);
insert into order_data values (2,'a','A-1',80);
insert into order_data values (3,'b','C',70);
insert into order_data values (4,'a','A-2',90);
insert into order_data values (5,'b','D',85);
insert into order_data values (6,'b','B',75);
insert into order_data values (7,'b','E',30);
insert into order_data values (8,'b','B-1',50);
insert into order_data values (9,'a','F',95);
insert into order_data values (10,'b','G',65);

with  x as (
     select
     id, city, name, score,
           if( instr(name,'-'),substr(name,1,1),name  ) as base_name
     from order_data
)
select
x.id,x.city,x.name,
x.score,x.base_name,order_data.score
from order_data join x  on  order_data.name  = x.base_name
order by x.city,order_data.score desc,x.id;

最后编辑于：2022.06.26 17:53:57

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