MySQL数据库表的数据插入、修改、删除、查询操作及实例应用

一、MySQL数据库表的数据插入、修改、删除和查询

 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;

操作SQL语法格式：

插入：insert

修改：update

删除：delete

查询：select

二、设计型实验三

1.创建表

 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','','');

2.查询student表的操作

#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;

3.两表综合查询

#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%';

这个查询同时参加计算机和英语考试的学生信息难了我好久，下面提供三种做法：

#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');

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