MySQL综合练习

INSERT INTO t_student VALUES( 901,’张老大’, ‘男’,1985,’计算机系’, ‘北
京市海淀区’);
INSERT INTO t_student VALUES( 902,’张老二’, ‘男’,1986,’中文系’, ‘北京
市昌平区’);
INSERT INTO t_student VALUES( 903,’张三’, ‘女’,1990,’中文系’, ‘湖南省
永州市’);
INSERT INTO t_student VALUES( 904,’李四’, ‘男’,1990,’英语系’, ‘辽宁省
阜新市’);
INSERT INTO t_student VALUES( 905,’王五’, ‘女’,1991,’英语系’, ‘福建省
厦门市’);
INSERT INTO t_student VALUES( 906,’王六’, ‘男’,1988,’计算机系’, ‘湖南
省衡阳市’);
INSERT INTO t_score VALUES(NULL,901, ‘计算机’,98);
INSERT INTO t_score VALUES(NULL,901, ‘英语’, 80);
INSERT INTO t_score VALUES(NULL,902, ‘计算机’,65);
INSERT INTO t_score VALUES(NULL,902, ‘中文’,88);
INSERT INTO t_score VALUES(NULL,903, ‘中文’,95);
INSERT INTO t_score VALUES(NULL,904, ‘计算机’,70);
INSERT INTO t_score VALUES(NULL,904, ‘英语’,92);
INSERT INTO t_score VALUES(NULL,905, ‘英语’,94);
INSERT INTO t_score VALUES(NULL,906, ‘计算机’,90);
INSERT INTO t_score VALUES(NULL,906, ‘英语’,85);

1.写出两张表
DROP TABLE IF EXISTS t_student;
CREATE TABLE t_student(
id INT(10) PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(20) NOT NULL,
sex VARCHAR (4),
birth YEAR,
department VARCHAR(20) NOT NULL,
address VARCHAR(50)
);

DROP TABLE IF EXISTS t_score;
CREATE TABLE t_score(
id INT(10) PRIMARY KEY AUTO_INCREMENT,
stu_id INT(10) NOT NULL,
c_name VARCHAR(20),
grade INT(20)
);

2– 查询student表的所有记录
SELECT * FROM t_student ;

3– 查询student表的第2条到4条记录
SELECT * FROM t_student LIMIT 1,3;

4– 从student表查询所有学生的学号（id）、姓名（name）和院系（department）的信息
SELECT id, name, department FROM t_student;

5– 从student表中查询计算机系和英语系的学生的信息（用 IN 关键字）
SELECT * FROM t_student WHERE department in (‘计算机系’,’英语系’);

6– 从student表中查询年龄18~22岁的学生信息（用 BETWEEN AND）
SELECT * FROM t_student WHERE (year(NOW())-birth) BETWEEN 18 AND 27;

7– 从student表中查询每个院系有多少人
SELECT department,COUNT(*) FROM t_student GROUP BY department;

8– 从score表中查询每个科目的最高分
SELECT c_name,MAX(grade) FROM t_score GROUP BY c_name;

9– 查询李四的考试科目（c_name）和考试成绩（grade）
SELECT s.name, sc.c_name AS ‘考试科目’,sc.grade AS ‘考试成绩’
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
WHERE name=’李四’;

10– 用连接的方式查询所有学生的信息和考试信息
SELECT*
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id;

11– 计算每个学生的总成绩
SELECT name,sum(grade)
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
GROUP BY s.name;

12– 计算每个考试科目的平均成绩
SELECT c_name,AVG(grade)
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
GROUP BY sc.c_name;

13– 查询计算机成绩低于95的学生信息
SELECT *
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
WHERE c_name = ‘计算机’ AND grade<95;

SELECT *
FROM t_student
WHERE id in
(SELECT stu_id FROM t_score
WHERE c_name= ‘计算机’AND grade < 95 );

)

14– 查询同时参加计算机和英语考试的学生的信息
SELECT *
FROM t_student
WHERE id IN
(SELECT stu_id FROM t_score
WHERE stu_id in(
SELECT stu_id FROM t_score
WHERE c_name = ‘计算机’) AND c_name = ‘英语’);

15– 将计算机考试成绩按从高到低进行排序
SELECT c_name,grade
FROM t_score
WHERE c_name = ‘计算机’
ORDER BY grade DESC;

16– 从student表和score表中查询出学生的学号，然后合并查询结果
SELECT name, sc.stu_id AS ‘学生学号’
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id;

17– 查询姓张或者姓王的同学的姓名、院系和考试科目及成绩
SELECT name, department,c_name,grade
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
WHERE name like ‘王%’OR name LIKE ‘张%’;

18– 查询都是湖南的学生的姓名、年龄、院系和考试科目及成绩
SELECT name, (year(NOW())- birth) as age,department,grade
FROM t_student AS s
LEFT JOIN t_score AS sc
ON s.id = sc.stu_id
WHERE address like ‘湖南%’;