ZYXGW的博客

Mysql必练50题（第十天）

ZYXGW — Thu, 25 Nov 2021 10:00:07 +0800

第四十六天查询各学生的年龄(周岁) select s_id,s_name,s_birth,if( month(current_date()) < month(s_birth) or (month(current_date()) = month(s_birth) and day(current_date()) < day(s_birth)), year(current_date()) - year(s_birth) -1, year(current_

Mysql必练50题（第九天）

ZYXGW — Wed, 24 Nov 2021 14:11:46 +0800

第四十一题查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩 select s_id,c_id,s_score from score where s_score in (select s_score from score group by s_score having count(*)>1); 第四十二题查询每门课程成绩最好的前三名 select sc.c_id,c.c_name,s.s_id,s.s_name,sc.s_score from student s inner join

Mysql必练50题练习（第八天）

ZYXGW — Tue, 23 Nov 2021 19:49:20 +0800

第三十六题查询任何一门课程成绩在70分以上的学生姓名、课程名称和分数 select s.s_name,c.c_name,sc.s_score from student s inner join score sc on s.s_id = sc.s_id inner join course c on sc.c_id = c.c_id group by sc.s_id having sc.s_score>70; 第三十七题查询课程不及格的学生 select s.s_name,c.c_name,

Mysql必练50题（第七天）

ZYXGW — Mon, 22 Nov 2021 12:13:46 +0800

第三十一题 select * from student where year(s_birth) = 1990; 第三十二题查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列 select sc.c_id,round(avg(sc.s_score),2) as avg_score,c.c_name from score sc left join course c on sc.c_id = c.c_id group by sc.c_id order by avg_scor

Mysql必练50题（第六天）

ZYXGW — Sun, 21 Nov 2021 12:58:21 +0800

第二十六题查询每门课程被选修的学生数 select sc.c_id,c.c_name,count(*) as cnt from score sc left join course c on sc.c_id = c.c_id group by sc.c_id; 第二十七题查询出只有两门课程的全部学生的学号和姓名 select s.s_id,s.s_name from student s inner join score sc on s.s_id = sc.s_id group by sc.s_

Mysql必练50题第五天

ZYXGW — Fri, 19 Nov 2021 20:43:17 +0800

第二十一题查询不同老师所教不同课程平均分从高到低显示 select t_name,c_name,round(avg(sc.s_score),2) as avg_score from score sc left join course c on sc.c_id = c.c_id left join teacher t on c.t_id = t.t_id group by t.t_id order by avg_score desc; 第二十二题查询所有课程的成绩第2名到第3名的学生信息及该课程成

Mysql必练50题（第四天）

ZYXGW — Tue, 16 Nov 2021 10:53:17 +0800

第十六题检索"01"课程分数小于60，按分数降序排列的学生信息 select * from student where s_id in (select s_id from score where c_id = 1 and s_score < 60); 第十七题 select s.s_id,s.s_name, sum(case c_id when 1 then s_score else 0 end) as "语文", sum(case c_id when 2 then s_score else

Mysql必练50题（第三天）

ZYXGW — Mon, 15 Nov 2021 14:21:42 +0800

第十一题查询没有学全所有课程的同学的信息 select s.* from student s left join score sc on s.s_id = sc.s_id group by s_id having count(*)<3; 第十二题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 s.* from student s inner join score sc on s.s_id = sc.s_id where c_id in (select

Mysql必练50题（第二天）

ZYXGW — Sun, 14 Nov 2021 15:39:44 +0800

第六题查询"李"姓老师的数量 select t_name,count(*) from teacher where t_name like "李%"; 第七题查询学过"张三"老师授课的同学的信息 select s.* from student s inner join score sc on s.s_id = sc.s_id inner join course c on sc.c_id = c.c_id inner join teacher t on c.t_id = t.t_id where t

MYSQL必练50题（第一天）

ZYXGW — Sat, 13 Nov 2021 20:46:26 +0800

一、表和库的建立 create database mysql_test; use mysql_test; drop table student; drop table score; drop table course; drop table teacher; create table student( s_id int, s_name varchar(8), s_birth date, s_sex varchar(4) ); insert into stu

爬虫基础

ZYXGW — Sun, 13 Sep 2020 18:41:23 +0800

小白一枚，最近开始学习爬虫。跟大家分享一下。本文以爬取python100例为对象一、爬虫的匹配方式有四种 1、正则表达式 2、CSS 3、beautiful soup 4、xpath 二、爬虫的基本步骤如下：第一步：先获取url((URL，是指“Uniform Resource Locator”的缩写，即统一bai资源定位符。))，表示网址 from bs4 import BeautifulSoup#导入所需要的包 import requests import pandas as pd url =