每日打卡

1.Python

1. List Comprehension:

2. OddNums

2.SQL

3.ML

1.The normal distribution, a normal distribution sample

The normal distribution is the most important probability distribution in statistics because it fits many natural phenomena. ... It is also known as the Gaussian distribution and the bell curve. The normal distribution is a probability function that describes how the values of a variable are distributed.

2. What is regularization?   

Regularization is a technique used in Statistics to solve overfitting problems.

4.job

converge, ZocDoc, white ops, Michael Kors,
Roku, Guardian Life, AHN/RHS, public goods, Horizon Media, Amnet, Dentsu Aegis Network 

sql语句练习50题(自己的答案)

-- 7、查询学过"张三"老师授课的同学的信息

select a.*from Student a
inner join Score b on a.s_id = b.s_id

inner join Teacher c on b.c_id =c.t_id

where c.t_name = '张三';

查询没学过"张三"老师授课的同学的信息
select d.*
from Student d
where d.s_name not in (select a.s_name from Student a
inner join Score b on a.s_id = b.s_id
inner join Teacher c on b.c_id =c.t_id
where c.t_name = '张三');

-- 11、查询没有学全所有课程的同学的信息

select a.*from Student a
where a.s_id not in (select s_id from Score where c_id='01')
   or a.s_id not in (select s_id from Score where c_id='02')
   or a.s_id not in (select s_id from Score where c_id='03');

#查询至少有一门课与学号为"01"的同学所学相同的同学的信息select distinct a.*from Student a , Score b
where a.s_id= b.s_id and  b.c_id in (select c_id from Score  where s_id= '01');


-- 14、查询没学过"张三"老师讲授的任一门课程的学生姓名select s_namefrom student
 where s_name not in (select a.s_namefrom Student a,Score b , Course c, Teacher d
where a.s_id= b.s_id and b.c_id = c.c_id and c.t_id=d.t_id and d.t_name ='张三')






#- 16、检索"01"课程分数小于60，按分数降序排列的学生信息
select a.* ,b.c_id, b.s_score
from Student a , Score b
where a.s_id = b.s_id and a.s_id in (select s_id from Score where c_id = '01' and s_score<60) and b.c_id = '01'
order by b.s_score DESC 

select t.s_score,(select count(s.s_score)+1 from Score as s  where s.s_score>t.s_score) as rank1
from Score as t
order by t.s_score desc;

-- 19、按各科成绩进行排序，并显示排名(实现不完全)


select c.s_id , c.c_id, c.s_score , count(d.s_score)+1 s_rank
from score c
left join Score d
on c.s_score < d.s_score  AND c.c_id=d.c_id
group by  c.c_id ,c.s_id
order by c.c_id ;

--20 不会做


select  a.s_id, a.sum_score ,count(b.sum_score)+1 rk
from (select  s_id, sum(s_score) sum_score from Score  group by s_id) a, (select  s_id, sum(s_score) sum_score from Score  group by s_id) b

where a.sum_score <= b.sum_score and a.s_id=b.s_id

  group by     a.s_id, a.sum_score
order by a.s_id;

-21
#查询不同老师所教不同课程平均分从高到低显示

select a.* ,avg(c.s_score)
from Teacher a , Course b,Score c

where a.t_id=b.t_id and b.c_id = c.c_id
group by  a.t_idorder by  avg(c.s_score) desc ;

select name , continent
from world a
where a.population>= all(select population*3 from world b where a. continent =b.continent)