/*案例1*/
create table students(
id int auto_increment not null primary key comment'ID',
name varchar(30) not null comment'名字',
email varchar(50) not null comment'郵箱',
address varchar(100) null default'北京' comment'地址'
);

--插入資料
insert into students(name,email,address) values('張飛','[email protected]',default),('
 
關羽','[email protected]','地獄');
insert into students(name,email,address,age,birth) values('張三','[email protected]',default,56,'1986-12-5'),('李四','[email protected]','地獄',26,'1888-9-2');
insert into students(name,email,address,age,birth) values('小明','[email protected]','大同',45,'1986-12-5'),('大龍','自己看@qq.com','南京',26,'1988-9-2
 
');

--給表新增列
alter table students add column phone varchar(11) not null comment '電話號碼';

--新增欄位內的值
update students set  phone=12338383388 where name='張飛';
update students set age=66 where name = '張飛';
update students set birth='1997-2-9' where name = '張飛';

--新增多個欄位
ALTER TABLE students
ADD COLUMN age int
 
(3) comment '年齡',
ADD COLUMN birth VARCHAR(255) comment '生日';


--新增多個欄位值
update students set age=85,birth='1993-9-9' where name='關羽';

--修改欄位中的型別
alter table students modify phone varchar(25) null ;

--刪除表裡的欄位
alter table students drop column phone;

--檢索欄位名並升序排列
select name,age from students order by age;

--檢索案例表裡條件age欄位為21到60的所有內容按age升序排列:
select * from students where age<=60 and age>=21 order by age;

--檢索案例表裡條件address欄位為北京或地獄並age欄位大於等於23的所有資訊並按升序排列
select * from students where(address='北京' or address='地獄') and age >= 25 order by age;

--檢索案例表裡條件age欄位不是21和50的name,age,address資訊並絳序排列:
select name,age,address from students where age not in (21,50) order by age desc;

--檢索案例表裡搜尋條件name欄位為張…的所有內容:
select * from students where name like '%張%';

--檢索案例表裡總人數的數量,最小年齡,最大年齡,年齡總和,平均值並起別名:
select count(*) as 總人數,min(age) as 最小年齡,max(age) as 最大年齡,sum(age) as 總和,avg(age) as 平均值 from students;




/*案例2*/
--建立學生表student，插入6條記錄
CREATE TABLE student (
    stu_id INT(10) PRIMARY KEY,
    stu_name VARCHAR(20)NOT NULL,
    sex VARCHAR(2),
    birth YEAR,
    department VARCHAR(20),
    addr VARCHAR(50)
);

--插入資料
INSERT INTO student VALUES
( 901,'張飛', '男',1985,'計算機系', '河北省涿州市'),
( 902,'關羽', '男',1986,'中文系', '山西省運城市'),
( 903,'貂蟬', '女',1990,'中文系', '山西省忻州縣'),
( 904,'劉備', '男',1990,'英語系', '河北省涿州市'),
( 905,'小喬', '女',1991,'英語系', '安徽省潛山市'),
( 906,'趙雲', '男',1988,'計算機系', '河北省正定市');

--建立分數表score，插入10條記錄
CREATE TABLE score (
    score_id INT(10) PRIMARY KEY AUTO_INCREMENT ,
    stu_id INT(10) NOT NULL ,
    c_name VARCHAR(20) ,
    grade INT(10)
);

INSERT INTO score(stu_id,c_name,grade) VALUES(901, '計算機',98),
(901, '英語', 80),(902, '計算機',65),(902, '中文',88),
(903, '中文',95),(904, '計算機',70),(904, '英語',92),
(905, '英語',94),(906, '計算機',90),(906, '英語',85);


--從student表中查詢計算機系和英語系學生的資訊
select * from student where department in ('計算機系','英語系');
select * from student where department='計算機系' or department='英語系';

--從student表中查詢年齡25~28歲的學生資訊。
select stu_id,stu_name,sex, 2016-birth AS age,department,addr from student WHERE 2016-birth BETWEEN 25 AND 28;
SELECT stu_id,stu_name,sex,2016-birth AS age,department,addr FROM student WHERE 2016-birth>=25 AND 2016-birth<=28;

--在student表中統計每個院系各有幾個學生
select department as 院系 , count(stu_id) as 人數 from student group by department;

--查詢每個院系學生中的最高分
select max(grade),department from score  left join student on score.stu_id=student.stu_id group by department;

--查詢學生貂蟬的考試科目（c_name）和考試成績（grade）
select stu_name,c_name,grade from score left join student on score.stu_id=student.stu_id where stu_name='貂蟬';

--查詢計算機成績低於95的學生資訊。
select stu_name,sex,birth,addr,department,c_name,grade from student left join score on score.stu_id=student.stu_id where c_name='計算機' and grade<=95;

--查詢同時參加計算機和英語考試的學生的資訊。
select * from student where stu_id=any(
    select stu_id from score where stu_id in
     (select stu_id from score where c_name='計算機') and c_name='英語'
    );

--從student表和score表中分別查詢出學生的學號，然後合併查詢結果。
select stu_id from student union select stu_id from score;

--查詢姓張或者姓趙的同學的個人資訊、院系和考試科目及成績。
select student.stu_id, stu_name,sex,birth, department,addr, c_name,grade from student,score  
 where (stu_name like "張%" or stu_name like "趙%") and (student.stu_id=score.stu_id);

 --查詢山西省的學生的姓名、出生年份、院系、考試科目及成績
 SELECT stu_name,birth,department, addr,c_name,grade from student,score where addr like "山西%"  and student.stu_id=score.stu_id;