【数据分析】MySQL常用语句及实战操作汇总

摘要

首先，在使用MySQL之前，弄清楚SQL和MySQL是什么关系？SQL它是一种用于操作数据库的语言。SQL是用于所有数据库的基本语言。不同数据库之间存在较小的语法更改，但基本的SQL语法基本保持不变。SQL是S tructured Q uery Language 的简短缩写。MySQL是一种RDBMS，它允许保持数据库中存在的数据。简单地说，SQL是一种查询语言，而MYSQL是数据库软件。本文主要记录MySQL语言的使用方法，为大家提供方便。

1.常用操作数据库的指令

功能实现	命令
1.查看所有的数据库	show databases;
2.创建一个叫datamp的数据库	create database datamp;
3.删除一个叫datamp的数据库	drop database datamp;
4.选中要使用的数据库	use datamp;
5.展示数据库中所有的表	show tables;
6.创建名为mp_table的表	create mp_table(字段1 类型，字段2 类型)
7.删除名为mp_table的表	drop table mp_table
8.查看创建库datamp的详细信息	show create database datamp
9.查看创建表datamp的详细信息	show create table datamp

2.对表操作的命令

功能实现	命令
1.修改字段类型	alter table 表名 modify 字段 字段类型
2.添加新的字段	alter table 表名 add 字段 字段类型
3.添加字段并指定位置	alter table 表明 add 字段 字段类型 after 字段
4.删除表字段	alter table 表名 drop 字段名
5.修改指定的字段	alter table 表名 change 原字段名字 新字段名字 字段类型

3.对数据操作的命令

功能实现	命令
1.增添数据	方法1：insert into 表名 values(值1，值2…)
-	方法2：insert into 表名(字段1，字段2…) values(值1，值2…)
-	方法3：insert into 表名(字段1，字段2…) values(值1，值2…)，(值1，值2…) …
2.删除数据	delect from 表名 where 条件
3.更新数据	update 表名 set 字段1=值1，字段2=值2 where 条件
4.查询数据	查询所有数据：select * from 表名
-	查询指定数据：select 字段 from 表名 where 条件
5.排序	select 字段 from 表名 order by 字段(desc/asc默认升序)
6.常用统计函数	sum,avg,count,max,min
7. 取数	select * from 表名 limit 偏移基准，数量

4.多表联合查询

功能实现	命令
内连接	select username from user inner join goods on user.gid=goods.gid;
左连接	select username from user left join goods on user.gid=goods.gid;
右连接	select username from user right join goods on user.gid=goods.gid;
嵌套查询	select username from user where gid in(select gid from goods)

5.实战操作汇总（参考知乎SQL 必会50道面试题）

数据表：

学生表：
Student(s_id,s_name,s_birth,s_sex) –学生编号,学生姓名, 出生年月,学生性别
课程表：
Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号
教师表：
Teacher(t_id,t_name) –教师编号,教师姓名
成绩表：
Score(s_id,c_id,s_s_score) –学生编号,课程编号,分数
创建表：

测试数据

–建表
–学生表
CREATE TABLE Student(
s_id VARCHAR(20),
s_name VARCHAR(20) NOT NULL DEFAULT ‘’,
s_birth VARCHAR(20) NOT NULL DEFAULT ‘’,
s_sex VARCHAR(10) NOT NULL DEFAULT ‘’,
PRIMARY KEY(s_id)
);
–课程表
CREATE TABLE Course(
c_id VARCHAR(20),
c_name VARCHAR(20) NOT NULL DEFAULT ‘’,
t_id VARCHAR(20) NOT NULL,
PRIMARY KEY(c_id)
);
–教师表
CREATE TABLE Teacher(
t_id VARCHAR(20),
t_name VARCHAR(20) NOT NULL DEFAULT ‘’,
PRIMARY KEY(t_id)
);
–成绩表
CREATE TABLE Score(
s_id VARCHAR(20),
c_id VARCHAR(20),
s_score INT(3),
PRIMARY KEY(s_id,c_id)
);

插入数据

–插入学生表测试数据
insert into Student values(‘01’ , ‘赵雷’ , ‘1990-01-01’ , ‘男’);
insert into Student values(‘02’ , ‘钱电’ , ‘1990-12-21’ , ‘男’);
insert into Student values(‘03’ , ‘孙风’ , ‘1990-05-20’ , ‘男’);
insert into Student values(‘04’ , ‘李云’ , ‘1990-08-06’ , ‘男’);
insert into Student values(‘05’ , ‘周梅’ , ‘1991-12-01’ , ‘女’);
insert into Student values(‘06’ , ‘吴兰’ , ‘1992-03-01’ , ‘女’);
insert into Student values(‘07’ , ‘郑竹’ , ‘1989-07-01’ , ‘女’);
insert into Student values(‘08’ , ‘王菊’ , ‘1990-01-20’ , ‘女’);
–课程表测试数据
insert into Course values(‘01’ , ‘语文’ , ‘02’);
insert into Course values(‘02’ , ‘数学’ , ‘01’);
insert into Course values(‘03’ , ‘英语’ , ‘03’);

–教师表测试数据
insert into Teacher values(‘01’ , ‘张三’);
insert into Teacher values(‘02’ , ‘李四’);
insert into Teacher values(‘03’ , ‘王五’);

–成绩表测试数据
insert into Score values(‘01’ , ‘01’ , 80);
insert into Score values(‘01’ , ‘02’ , 90);
insert into Score values(‘01’ , ‘03’ , 99);
insert into Score values(‘02’ , ‘01’ , 70);
insert into Score values(‘02’ , ‘02’ , 60);
insert into Score values(‘02’ , ‘03’ , 80);
insert into Score values(‘03’ , ‘01’ , 80);
insert into Score values(‘03’ , ‘02’ , 80);
insert into Score values(‘03’ , ‘03’ , 80);
insert into Score values(‘04’ , ‘01’ , 50);
insert into Score values(‘04’ , ‘02’ , 30);
insert into Score values(‘04’ , ‘03’ , 20);
insert into Score values(‘05’ , ‘01’ , 76);
insert into Score values(‘05’ , ‘02’ , 87);
insert into Score values(‘06’ , ‘01’ , 31);
insert into Score values(‘06’ , ‘03’ , 34);
insert into Score values(‘07’ , ‘02’ , 89);
insert into Score values(‘07’ , ‘03’ , 98);

如图：

1.查找姓“张”老师的数量

select count(t_name) from teacher where t_name like '张%';

2.查询课程编号为“01”的课程比“02”的课程成绩高的所有学生的学号

select a.s_id "s_no",st.s_name,a.s_score "01",b.s_score "02" FROM
(select s_id,c_id,s_score from score WHERE c_id='01')as a
INNER JOIN
(select s_id,c_id,s_score from score WHERE c_id='02')as b
on a.s_id=b.s_id
INNER JOIN student as st on st.s_id = a.s_id
where a.s_score>b.s_score

3.查询平均成绩大于60分的学生的学号和平均成绩

select s_id,avg(s_score) from score GROUP BY s_id HAVING avg(s_score)>60

4.查询所有学生的学号、姓名、选课数、总成绩

select st.s_id,st.s_name,count(sc.s_id),sum(sc.s_score) from student as st
INNER JOIN score as sc on st.s_id=sc.s_id
GROUP BY st.s_id,st.s_name

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5.查询没学过“张三”老师课的学生的信息

select * from student 
where s_id not in
(select sc.s_id from teacher as t
INNER JOIN course as c on t.t_id=c.t_id
INNER JOIN score as sc on c.c_id=sc.c_id
where t.t_name='张三')

6.查询学过“张三”老师所教的所有课的同学信息

where s_id in
(select sc.s_id from teacher as t
INNER JOIN course as c on t.t_id=c.t_id
INNER JOIN score as sc on c.c_id=sc.c_id
where t.t_name='张三')

7.查询学过编号为“01”的课程并且也学过编号为“02”的课程的学生的学号、姓名

方法1：
select * from student 
where s_id in
(select a.s_id from
(select s_id,c_id from score where c_id='02')as a
INNER JOIN 
(select s_id,c_id from score where c_id='01') as b
on a.s_id=b.s_id
)

方法2：
select * from student 
where s_id in
(select s_id from score where c_id='01')
AND s_id in
(select s_id from score where c_id='02')

8.查询学过编号为“01”的课程且没有学过编号为“02”的课程的学生的信息

select * from student 
where s_id in
(select s_id from score where c_id='01')
AND s_id NOT in
(select s_id from score where c_id='02')

9.查询课程编号为“02”的总成绩

select sum(s_score) from score 
where c_id='02'

10.查询所有课程成绩小于60分的学生的信息

SELECT st.* from
(select s_id,count(s_id)"cnt" from score
where s_score<60
GROUP BY s_id)
as a
INNER JOIN
(select s_id,COUNT(c_id)"cnt2" from score
group BY s_id)
as b 
on a.s_id=b.s_id
INNER JOIN
student as st on st.s_id=b.s_id
where a.cnt=b.cnt2

11.查询没有学全所有课的学生的信息

select st.* from student as st
INNER JOIN score as sc 
on sc.s_id=st.s_id
GROUP BY st.s_id,st.s_name HAVING COUNT(c_id)<(select COUNT(DISTINCT c_id)from course)

12.查询至少有一门课与学号为“01”的学生所学课程相同的学生信息

select DISTINCT st.*
from student as st
INNER JOIN score as sc on sc.s_id=st.s_id
where sc.c_id in (select c_id from score where s_id='01')
and st.s_id != '01'

13.查询和“01”号同学所学课程完全相同的其他同学的信息

select DISTINCT st.s_id,st.s_name
from student as st
INNER JOIN score as sc on sc.s_id=st.s_id
GROUP BY st.s_id HAVING COUNT(sc.c_id) in (select count(c_id) from score where s_id='01')
and st.s_id != '01'

14.查询没学过"张三"老师讲授的任一门课程的学生信息

select *
from student 
where s_id not in
(select s_id from score as sc 
INNER JOIN
course as c on c.c_id=sc.c_id
INNER JOIN
teacher as t on t.t_id=c.t_id
where t_name = '张三'
)

15.查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

select st.* from student as st
INNER JOIN score as sc on st.s_id=sc.s_id
where sc.s_score<60
GROUP BY st.s_id
HAVING COUNT(c_id)>=2

16.检索"01"课程分数小于60，按分数降序排列的学生信息

select st.*,sc.* from student as st
INNER JOIN score as sc on sc.s_id=st.s_id
where sc.c_id='01' and sc.s_score<60
ORDER BY sc.s_score DESC

17.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

select s_id,avg(s_score),
MAX(case when c_id='01' then s_score else null end)"语文" ,
MAX(case when c_id='02' then s_score else null end)"数学" ,
MAX(case when c_id='03' then s_score else null end)"英语" 
from score
group BY s_id
ORDER BY avg(s_score) desc

18.查询各科成绩最高分、最低分和平均分：以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率
–及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90
–体会下avg，sum的使用区别

select c.c_id'课程id',
c.c_name'课程名称',
max(sc.s_score)'最大值',
min(sc.s_score)'最小值',
avg(sc.s_score)'平均值',
sum(case WHEN sc.s_score>=60 then 1 else 0 end)/count(s_id)"及格",
avg(case when sc.s_score>=70 and sc.s_score<80 then 1 else 0 end) "中等",
avg(case when sc.s_score>=80 and sc.s_score<90 then 1 else 0 end) "优良",
avg(case when sc.s_score>=90 then 1 else 0 end) "优秀"
from score as sc
INNER JOIN course as c 
on c.c_id=sc.c_id
GROUP BY c.c_id

19.查询学生的总成绩并进行排名

select s_id,sum(s_score) from score
GROUP BY s_id
ORDER BY sum(s_score) DESC

20.查询不同老师所教不同课程平均分从低到高显示

# 以课程为主题
select sc.c_id,c.c_name,avg(sc.s_score) 
from score as sc
INNER JOIN course as c 
on c.c_id=sc.c_id
GROUP BY sc.c_id
ORDER BY avg(sc.s_score)

# 以老师为主题
select t.t_id,t.t_name,avg(sc.s_score) 
from score as sc
INNER JOIN course as c 
on c.c_id=sc.c_id
INNER JOIN teacher as t
on t.t_id=c.t_id
GROUP BY t.t_id
ORDER BY avg(sc.s_score)

21.使用分段[100-85],[85-70],[70-60],[<60]来统计各科成绩，分别统计各分数段人数：课程ID和课程名称

select c.c_id,c.c_name,
sum(case when sc.s_score<=100 and sc.s_score>85 then 1 else 0 end)"[100,85)",
sum(case when sc.s_score<=85 and sc.s_score>70 then 1 else 0 end)"[85,70)",
count(CASE when sc.s_score<=70 and sc.s_score>60 then 1 else null end)"[70,60)",
count(CASE when sc.s_score<=60 then 1 else null end)"[60,0)"
from score as sc
INNER JOIN course as c on sc.c_id=c.c_id
GROUP BY c.c_id

22.查询每门课程被选修的学生数

select c_id,count(c_id) from score
group BY c_id

23.查询出只有两门课程的全部学生的学号和姓名

select st.* from score as sc
INNER JOIN student as st
on st.s_id=sc.s_id
GROUP BY st.s_id HAVING COUNT(sc.c_id)=2

24.查询男生、女生人数

select count(s_id)
from student 
GROUP BY s_sex

25.查询1990年出生的学生名单

#方法1
select * from student
where YEAR(s_birth)=1990
# 方法2
select * from student
where s_birth like '1990%'

26.查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

select st.s_id,st.s_name,avg(sc.s_score) from student as st
INNER JOIN score as sc on sc.s_id=st.s_id
GROUP BY st.s_id HAVING avg(sc.s_score)>85

27.查询所有学生的课程及分数情况

select sc.s_id,
max(case WHEN c.c_name="语文" then sc.s_score else null end)"语文",
max(case WHEN c.c_name="数学" then sc.s_score else null end)"数学",
max(case WHEN c.c_name="英语" then sc.s_score else null end)"英语"
from score as sc
INNER JOIN course as c
on c.c_id=sc.c_id
GROUP BY sc.s_id

28.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 a.*,b.*,c.*
from
(select s_id,c_id,s_score from score where c_id='01')as a
INNER JOIN
(select s_id,c_id,s_score from score where c_id='02')as b
on a.s_id=b.s_id
INNER JOIN
(select s_id,c_id,s_score from score where c_id='03')as c
on b.s_id=c.s_id
WHERE a.s_score=b.s_score and b.s_score=c.s_score

29. 查询选修了全部课程的学生信息

select s_id,count(c_id) from score
GROUP BY s_id
HAVING count(c_id)=(select count(*) from course)

30.查询5月过生日的学生

select * from student
where MONTH(s_birth)=MONTH("2022/5/10")

到此，我完整地复现了MySQL的重要操作，方便大家学习，希望对大家有所帮助。