MySQL——查询练习（1）

一、数据准备

学生表student：学号，姓名，性别，出生年月日，所在班级

create table student(
	sno varchar(20) primary key,
	sname varchar(20) not null,
	ssex varchar(10) not null,
	sbirthday datetime,
	class varchar(20)
);

课程表course：课程号，课程名称，教师编号（外键）

create table course(
	cno varchar(20) primary key,
	cname varchar(20) not null,
	tno varchar(20) not null,
	foreign key(tno) references teacher(tno)
);

成绩表score：学号，课程号，成绩

create table score(
	sno varchar(20) not null,
	cno varchar(20) not null,
	degree decimal,
	foreign key(sno) references student(sno),
	foreign key(cno) references course(cno),
	primary key(sno,cno)
);

教师表teacher：教师编号，教师名字，教师性别，出生年月日，职称，所在部门

create table teacher(
	tno varchar(20) primary key,
	tname varchar(20) not null,
	tsex varchar(10) not null,
	tbirthday datetime,
	prof varchar(20) not null,
	depart varchar(20) not null
);

向数据表中添加信息：

--学生表数据
INSERT INTO student VALUES('101','曾华','男','1977-09-01','95033');
INSERT INTO student VALUES('102','匡明','男','1975-10-02','95031');
INSERT INTO student VALUES('103','王丽','女','1976-01-23','95033');
INSERT INTO student VALUES('104','李军','男','1976-02-20','95033');
INSERT INTO student VALUES('105','王芳','女','1975-02-10','95031');
INSERT INTO student VALUES('106','陆军','男','1974-06-03','95031');
INSERT INTO student VALUES('107','王尼玛','男','1976-02-20','95033');
INSERT INTO student VALUES('108','张全蛋','男','1975-02-10','95031');
INSERT INTO student VALUES('109','赵铁柱','男','1974-06-03','95031');

--教师表数据
INSERT INTO teacher VALUES('804','李诚','男','1958-12-02','副教授','计算机系');
INSERT INTO teacher VALUES('856','张旭','男','1969-03-12','讲师','电子工程系');
INSERT INTO teacher VALUES('825','王萍','女','1972-05-05','助教','计算机系');
INSERT INTO teacher VALUES('831','刘冰','女','1977-08-14','助教','电子工程系');

--添加课程表
INSERT INTO course VALUES('3-105','计算机导论','825');
INSERT INTO course VALUES('3-245','操作系统','804');
INSERT INTO course VALUES('6-166','数字电路','856');
INSERT INTO course VALUES('9-888','高等数学','831');

--添加成绩表
INSERT INTO score VALUES('103','3-245','86');
INSERT INTO score VALUES('105','3-245','75');
INSERT INTO score VALUES('109','3-245','68');
INSERT INTO score VALUES('103','3-105','92');
INSERT INTO score VALUES('105','3-105','88');
INSERT INTO score VALUES('109','3-105','76');
INSERT INTO score VALUES('103','6-166','85');
INSERT INTO score VALUES('105','6-166','79');
INSERT INTO score VALUES('109','6-166','81');

二、查询练习（从1到10）

1.查询student表中所有（*）记录

select * from student;
+-----+-----------+------+---------------------+-------+
| sno | sname     | ssex | sbirthday           | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华      | 男   | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明      | 男   | 1975-10-02 00:00:00 | 95031 |
| 103 | 王丽      | 女   | 1976-01-23 00:00:00 | 95033 |
| 104 | 李军      | 男   | 1976-02-20 00:00:00 | 95033 |
| 105 | 王芳      | 女   | 1975-02-10 00:00:00 | 95031 |
| 106 | 陆军      | 男   | 1974-06-03 00:00:00 | 95031 |
| 107 | 王尼玛    | 男   | 1976-02-20 00:00:00 | 95033 |
| 108 | 张全蛋    | 男   | 1975-02-10 00:00:00 | 95031 |
| 109 | 赵铁柱    | 男   | 1974-06-03 00:00:00 | 95031 |

2.查询student表中所有记录的sname,ssex和class列

select sname,ssex,class from student;
+-----------+------+-------+
| sname     | ssex | class |
+-----------+------+-------+
| 曾华      | 男   | 95033 |
| 匡明      | 男   | 95031 |
| 王丽      | 女   | 95033 |
| 李军      | 男   | 95033 |
| 王芳      | 女   | 95031 |
| 陆军      | 男   | 95031 |
| 王尼玛    | 男   | 95033 |
| 张全蛋    | 男   | 95031 |
| 赵铁柱    | 男   | 95031 |
+-----------+------+-------+

3.查询教师所有的单位但是不重复的depart列（distinct）

select distinct depart from teacher;
+-----------------+
| depart          |
+-----------------+
| 计算机系        |
| 电子工程系      |
+-----------------+

4.查询score表中成绩(degree)在60-80之间所有的记录
查询区间：

使用between ... and ...，是包含边界的

select * from score where degree between 60 and 80;
+-----+-------+--------+
| sno | cno   | degree |
+-----+-------+--------+
| 105 | 3-245 |     75 |
| 105 | 6-166 |     79 |
| 109 | 3-105 |     76 |
| 109 | 3-245 |     68 |
+-----+-------+--------+

使用运算符

select * from score where degree > 60 and degree < 80;
+-----+-------+--------+
| sno | cno   | degree |
+-----+-------+--------+
| 105 | 3-245 |     75 |
| 105 | 6-166 |     79 |
| 109 | 3-105 |     76 |
| 109 | 3-245 |     68 |
+-----+-------+--------+

5.查询score表中成绩为85, 86, 或者88的记录（或者关系，in）

select * from score where degree in (85,86,88);
+-----+-------+--------+
| sno | cno   | degree |
+-----+-------+--------+
| 103 | 3-245 |     86 |
| 103 | 6-166 |     85 |
| 105 | 3-105 |     88 |
+-----+-------+--------+

6.查询student表中’95031’班或者性别为’女’的同学记录
不同字段间的或者，用 or

select * from student where class='95031' or ssex='女';
+-----+-----------+------+---------------------+-------+
| sno | sname     | ssex | sbirthday           | class |
+-----+-----------+------+---------------------+-------+
| 102 | 匡明      | 男   | 1975-10-02 00:00:00 | 95031 |
| 103 | 王丽      | 女   | 1976-01-23 00:00:00 | 95033 |
| 105 | 王芳      | 女   | 1975-02-10 00:00:00 | 95031 |
| 106 | 陆军      | 男   | 1974-06-03 00:00:00 | 95031 |
| 108 | 张全蛋    | 男   | 1975-02-10 00:00:00 | 95031 |
| 109 | 赵铁柱    | 男   | 1974-06-03 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+

7.以class降序查询student表中所有的记录
使用order by，升序为asc（默认升序），降序为desc。

select * from student order by class desc;
+-----+-----------+------+---------------------+-------+
| sno | sname     | ssex | sbirthday           | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华      | 男   | 1977-09-01 00:00:00 | 95033 |
| 103 | 王丽      | 女   | 1976-01-23 00:00:00 | 95033 |
| 104 | 李军      | 男   | 1976-02-20 00:00:00 | 95033 |
| 107 | 王尼玛    | 男   | 1976-02-20 00:00:00 | 95033 |
| 102 | 匡明      | 男   | 1975-10-02 00:00:00 | 95031 |
| 105 | 王芳      | 女   | 1975-02-10 00:00:00 | 95031 |
| 106 | 陆军      | 男   | 1974-06-03 00:00:00 | 95031 |
| 108 | 张全蛋    | 男   | 1975-02-10 00:00:00 | 95031 |
| 109 | 赵铁柱    | 男   | 1974-06-03 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+

8.以cno升序、degree降序查询score表中所有的数据
先以cno升序排序，相同时再按照degree降序排序。

select * from score order by cno asc,degree desc;
+-----+-------+--------+
| sno | cno   | degree |
+-----+-------+--------+
| 103 | 3-105 |     92 |
| 105 | 3-105 |     88 |
| 109 | 3-105 |     76 |
| 103 | 3-245 |     86 |
| 105 | 3-245 |     75 |
| 109 | 3-245 |     68 |
| 103 | 6-166 |     85 |
| 109 | 6-166 |     81 |
| 105 | 6-166 |     79 |
+-----+-------+--------+

9.查询’95031’班的学生人数。（统计，count）

select count(*) from student where class='95031';
+----------+
| count(*) |
+----------+
|        5 |
+----------+

10.查询score表中的最高分数的学生号和课程号.(子查询)

select sno,cno from score where degree=(select max(degree) from score);
+-----+-------+
| sno | cno   |
+-----+-------+
| 103 | 3-105 |
+-----+-------+

实际步骤：

---第一步
select max(degree) from score;
---第二步
select sno,cno from score where degree=(查询到的值);

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