CREATE DATABASE db0504;

 USE db0504;

 CREATE TABLE student (

     sno VARCHAR (10) NOT NULL UNIQUE PRIMARY KEY,

     sname VARCHAR (20) NOT NULL,

     ssex enum ('男', '女') NOT NULL DEFAULT '男',

     sbirth date,

     sclass VARCHAR (10),

     zno CHAR (4)

 ) DEFAULT charset = gb2312;

 #添加操作

 INSERT INTO student

 VALUES('','丁暖','女','1993-9-9','物联网12-1','z002');

 INSERT INTO student (sno,sname,ssex,sbirth,sclass,zno)

 VALUES('','孔超','男','1993-9-19','自动化11-1','z006');

 INSERT INTO student (sno, sname, ssex, zno)

 VALUES('','韩梅','女','z006');

 INSERT INTO student (sname, zno, sno)

 VALUES('韩梅2','z006','');

 INSERT INTO student VALUES

 ('','孔超1','男','1993-9-19','自动化11-1','z006');

 ('','孔超2','男','1993-9-19','自动化11-1','z006');

 ('','孔超3','男','1993-9-19','自动化11-1','z006');

 ('','孔超4','男','1993-9-19','自动化11-1','z006');

 #修改操作

 UPDATE student

 SET sname = '张三',sbirth = '1993-6-19'

 WHERE sname = '丁暖';

 UPDATE student SET zno = LEFT (zno, 3);

 #删除操作

 delete from student

 where sname='张三';

 #查询操作

 SELECT * FROM student;#查询student表的所有记录

 SELECT sno,sname,ssex,sbirth FROM student;#查询部分字段信息

 SELECT * FROM student WHERE age BETWEEN 25 AND 30;

 #清空表操作

 truncate student;#高效

 delete from student;

 CREATE DATABASE homework;

 USE homework;

 CREATE TABLE student (

     Num INT (10) NOT NULL UNIQUE PRIMARY KEY,

     name VARCHAR(20) NOT NULL,

     Sex VARCHAR(4) NOT NULL,

     birthday DATETIME,

   bumen VARCHAR(20) NOT NULL,

   address VARCHAR(50)

 ) DEFAULT charset = gb2312;

 CREATE TABLE score (

   Id INT(10) NOT NULL UNIQUE PRIMARY KEY,

   C_name VARCHAR(20),

   Stu_id INT(10) NOT NULL,

   grade INT(10),

   CONSTRAINT score_fk FOREIGN KEY(Stu_id) REFERENCES student(Num)

 ) DEFAULT charset = gb2312;

 INSERT INTO student VALUES

 ('','张军','男','1985-1-1','计算机系','北京市海淀区'),

 ('','张超','男','1986-2-2','中文系','北京市昌平区'),

 ('','张美','女','1990-2-1','中文系','湖南省永州市'),

 ('','李五一','男','1990-2-3','英语系','辽宁省阜新市'),

 ('','王芳','女','1991-4-6','英语系','福建省厦门市'),

 ('','王桂','男','1988-6-7','计算机系','湖南省衡阳市');

 INSERT INTO score VALUES

 (1001,'计算机','',''),

 (1002,'英语','',''),

 (1003,'计算机','',''),

 (1004,'中文','',''),

 (1005,'中文','',''),

 (1006,'计算机','',''),

 (1007,'英语','',''),

 (1008,'英语','',''),

 (1009,'计算机','',''),

 (1010,'英语','','');

#查询student表的所有记录

SELECT * FROM student;

SELECT Num,name,Sex,birthday,bumen,address FROM student;

#查询student表的第2条到第4条记录

SELECT Num,name,Sex,birthday,bumen,address FROM student LIMIT 1,3;

#从student表中查询所有学生的学号、姓名和院系的信息

SELECT Num,name,bumen FROM student;

#查询计算机系和英语系学生的信息

SELECT * FROM student WHERE bumen IN('计算机系','英语系');

SELECT * FROM student WHERE bumen='计算机系' OR bumen='英语系';

#从student表中查询年龄为18-22岁学生的信息

ALTER TABLE student ADD age INT(4);

ALTER TABLE student MODIFY age INT(4) AFTER Sex;

UPDATE student SET age=24 WHERE Num=901;

UPDATE student SET age=23 WHERE Num=902;

UPDATE student SET age=19 WHERE Num=903;

UPDATE student SET age=19 WHERE Num=904;

UPDATE student SET age=18 WHERE Num=905;

UPDATE student SET age=21 WHERE Num=906;

SELECT * FROM student WHERE age BETWEEN 18 AND 22;

SELECT * FROM student WHERE age>=18 AND age<=22;

#从student表中查询每个院系有多少人，为统计的人数列取别名sum_of_bumen

SELECT bumen,COUNT(bumen) AS sum_of_bumen FROM student GROUP BY bumen;

#从score表中查询每个科目的最高分

SELECT C_name,MAX(grade) FROM score GROUP BY C_name;

#查询李五一的考试科目（C_name）和考试成绩（grade）

select C_name,grade from student left join score on student.Num=score.Stu_id where name='李五一';

#用连接查询的方式查询所有学生的信息和考试信息

select * from student left join score on student.Num=score.Stu_id;

#计算每个学生的总成绩（需显示学生姓名）

select name '姓名',SUM(grade) '总成绩' from student left join score on student.Num=score.Stu_id group by name;

#计算每个考试科目的平均成绩

select C_name '考试科目',AVG(grade) '平均成绩' from student left join score on student.Num=score.Stu_id group by C_name;

#查询计算机成绩低于95分的学生信息

select * from student left join score on student.Num=score.Stu_id where grade<95 AND C_name='计算机';

#将计算机成绩按从高到低排序

select grade '计算机成绩' from score where C_name='计算机' order by grade desc;#asc升序，desc降序

#从student表和score表中查询学生的学号，然后合并查询结果

select Num '学号' from student union select Stu_id from score;

#查询姓张或者姓王的同学的姓名、院系、考试科目和成绩

select name,bumen,C_name,grade from student left join score on student.Num=score.Stu_id where name like '张%' union

select name,bumen,C_name,grade from student left join score on student.Num=score.Stu_id where name like '王%';

#查询都是湖南的学生的姓名、年龄、院系、考试科目和成绩

select name,age,bumen,C_name,grade from student left join score on student.Num=score.Stu_id where address like '湖南%';

#查询同时参加计算机和英语考试的学生的信息做法一

select * from student where Num in (

select Stu_id from score where C_name ='计算机' and Stu_id in(select Stu_id from score where C_name ='英语'));

#查询同时参加计算机和英语考试的学生的信息做法二

SELECT a.* FROM student a,score b,score c WHERE a.Num=b.Stu_id AND b.C_name='计算机'

AND a.Num=c.Stu_id AND c.C_name='英语';

#查询同时参加计算机和英语考试的学生的信息做法三

SELECT * FROM student WHERE Num =ANY( SELECT Stu_id FROM score WHERE Stu_id IN (

SELECT Stu_id FROM score WHERE C_name='计算机') AND C_name='英语');