数据库试题

student表

score表

插入数据为：
INSERT INTO student VALUES( 901,'张老大', '男',1985,'计算机系', '北京市海淀区');
INSERT INTO student VALUES( 902,'张老二', '男',1986,'中文系', '北京市昌平区');
INSERT INTO student VALUES( 903,'张三', '女',1990,'中文系', '湖南省永州市');
INSERT INTO student VALUES( 904,'李四', '男',1990,'英语系', '辽宁省阜新市');
INSERT INTO student VALUES( 905,'王五', '女',1991,'英语系', '福建省厦门市');
INSERT INTO student VALUES( 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);
INSERT INTO score VALUES(NULL,901, '英语', 80);
INSERT INTO score VALUES(NULL,902, '计算机',65);
INSERT INTO score VALUES(NULL,902, '中文',88);
INSERT INTO score VALUES(NULL,903, '中文',95);
INSERT INTO score VALUES(NULL,904, '计算机',70);
INSERT INTO score VALUES(NULL,904, '英语',92);
INSERT INTO score VALUES(NULL,905, '英语',94);
INSERT INTO score VALUES(NULL,906, '计算机',90);
INSERT INTO score VALUES(NULL,906, '英语',85);

创建student表和score表
略

查询student表的所有记录
略

查询student表的第2条到4条记录

    SELECT * FROM student LIMIT 1,3;

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 student;

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');

从student表中查询年龄18~22岁的学生信息

    SELECT * FROM student 
    WHERE (year(now())-birth) BETWEEN 28 AND 32;

原题区间太小

    SELECT * FROM student WHERE (2017-birth) BETWEEN 28 AND 32;

从student表中查询每个院系有多少人

    SELECT department,count(id) FROM student GROUP BY department;

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;

查询李四的考试科目（c_name）和考试成绩（grade）

    SELECT sc.c_name,sc.grade FROM score AS sc
    LEFT JOIN student AS st ON st.id=sc.stu_id
    WHERE st.name='李四';

用连接的方式查询所有学生的信息和考试信息

    SELECT * FROM score as sc
    LEFT JOIN student as st 
    ON st.id= sc.stu_id;

计算每个学生的总成绩

    SELECT st.name,SUM(sc.grade) FROM score AS sc
    LEFT JOIN student AS  st 
    ON st.id= sc.stu_id
    GROUP BY sc.stu_id;

计算每个考试科目的平均成绩

    SELECT c_name,AVG(grade) FROM score GROUP BY c_name;

查询计算机成绩低于95的学生信息

    SELECT st.* FROM score AS sc 
    LEFT JOIN student AS st 
    ON st.id=sc.stu_id
    WHERE sc.c_name='计算机' AND sc.grade <95;

查询同时参加计算机和英语考试的学生的信息

    select * FROM score AS sc
    LEFT JOIN student AS st
    ON st.id=sc.stu_id
    GROUP BY sc.c_name

    /*select * FROM score AS sc1
    LEFT JOIN student AS st 
    ON st.id=sc1.stu_id
    WHERE sc1.c_name='计算机'  错误回答
    LEFT JOIN score AS sc2
    ON st.id=sc2.stu_id
    WHERE sc2.c_name='英语'*/

    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';

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;

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;

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 st.name,st.department,sc.c_name,sc.grade FROM score sc 
    LEFT JOIN student AS st ON st.id=sc.stu_id 
    WHERE st.`name` LIKE '张%' OR st.`name` LIKE '王%';

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 st.name,(year(now())-birth) AS '年龄',st.department,sc.c_name,sc.grade
    FROM score AS sc 
    LEFT JOIN student AS st 
    ON st.id = sc.stu_id
    WHERE st.address LIKE '%湖南%';

最后

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