mysql 查询 练习题及答案

CREATE DATABASE school;
USE school;
/*1.创建student表格*//*id为主键 非空 唯一 */
CREATE TABLE student (id INT(10) PRIMARY KEY NOT NULL UNIQUE,
uname VARCHAR(20) NOT NULL,
sex VARCHAR(4),
birth YEAR,
department VARCHAR(20),
address VARCHAR(50));
/*1.创建score表格*/
CREATE TABLE score (id INT(10) NOT NULL UNIQUE PRIMARY KEY AUTO_INCREMENT,
stu_id INT(10) NOT NULL,
c_name VARCHAR(20),
grade INT(10));
/*2.为student表格与score表格增加记录*/
INSERT INTO student VALUES (901,'张老大', '男',1985,'计算机系', '北京市海淀区'),
(902,'张老二', '男',1986,'中文系', '北京市昌平区'),
(903,'张三', '女',1990,'中文系', '湖南省永州市'),
(904,'李四', '男',1990,'英语系', '辽宁省阜新市'),
(905,'王五', '女',1991,'英语系', '福建省厦门市'),
(906,'王六', '男',1988,'计算机系', '湖南省衡阳市');
INSERT INTO score VALUES (NULL,901, '计算机',98),
(NULL,901, '英语', 80),
(NULL,902, '计算机',65),
(NULL,902, '中文',88),
(NULL,903, '中文',95),
(NULL,904, '计算机',70),
(NULL,904, '英语',92),
(NULL,905, '英语',94),
(NULL,906, '计算机',90),
(NULL,906, '英语',85);
/*3.查询student表的所有记录*/
SELECT * FROM student;
/*4.查询student表的第2条到4条记录*/
SELECT * FROM student LIMIT 1,3;
/*5.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,uname,department FROM student;
/*6.从student表中查询计算机系和英语系的学生的信息*/
SELECT * FROM student WHERE department IN('计算机系','英语系');
/*7.从student表中查询年龄18~22岁的学生信息*/
SELECT id,uname,sex,2019-birth,department,address FROM student
WHERE 2019-birth BETWEEN 24 AND 28;
/*或*/
SELECT id,uname,sex,2019-birth,department,address FROM student
WHERE 2019-birth>=24 AND 2019-birth<=28;
/*8.从student表中查询每个院系有多少人 */
SELECT department,COUNT(id) FROM student GROUP BY department;
/*9.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;
/*10.查询李四的考试科目（c_name）和考试成绩（grade）*/
SELECT c_name,grade FROM score WHERE stu_id=(SELECT id FROM student WHERE uname ='李四');
/*用连接的方式查询所有学生的信息和考试信息*/
SELECT student.id,uname,sex,birth,department,address,c_name,grade
FROM student,score WHERE student.id = score.stu_id;
/*12.计算每个学生的总成绩*/
SELECT student.id,uname,SUM(grade) FROM student,score
WHERE student.id = score.stu_id GROUP BY id;
/*13.计算每个考试科目的平均成绩*/
SELECT c_name,AVG(grade) FROM score GROUP BY c_name;
/*14.查询计算机成绩低于95的学生信息*/
SELECT * FROM student WHERE id IN (SELECT stu_id FROM score WHERE c_name='计算机' AND grade<95);
/*15.查询同时参加计算机和英语考试的学生的信息*/
SELECT * FROM student WHERE id = 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');
#或
SELECT a.* FROM student a,score b ,score c WHERE a.id = b.stu_id
AND b.c_name='计算机' AND a.id = c.stu_id AND c.c_name='英语';
/*16.将计算机考试成绩按从高到低进行排序*/
SELECT stu_id,grade FROM score WHERE c_name='计算机' ORDER BY grade DESC;
/*17.从student表和score表中查询出学生的学号，然后合并查询结果*/
SELECT id FROM student UNION SELECT stu_id FROM score;
/*18.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 student.id,uname,sex,birth,department,address,c_name,grade
FROM student,score WHERE (uname LIKE '张%' OR uname LIKE '王%') AND student.id=score.stu_id;
/*19.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 student.id,uname,sex,birth,department,address,c_name,grade
FROM student,score WHERE student.address LIKE '湖南%' AND student.id = score.stu_id;