student表:

score表:

向student表插入记录:

向score表插入记录:

1.查询student表的所有记录
SELECT * FROM student;2.查询student表的第2条到4条记录
SELECT * 
FROM student
LIMIT 1,3;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;4.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 = '计算机系' OR department = '英语系';5.从student表中查询年龄18~22岁的学生信息
SELECT *
FROM student
WHERE  YEAR(NOW()) - birth BETWEEN 18 AND 22;6.从student表中查询每个院系有多少人
SELECT department, count(*)
FROM student
GROUP BY department;7.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;8.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 name = '李四');9.用连接的方式查询所有学生的信息和考试信息
SELECT *
FROM student AS stu, score AS sco
WHERE sco.id = stu.id;10.计算每个学生的总成绩
SELECT stu_id, SUM(grade)
FROM score
GROUP BY stu_id;11.计算每个考试科目的平均成绩
SELECT c_name, AVG(grade)
FROM score
GROUP BY c_name;12.查询计算机成绩低于95的学生信息
SELECT *
FROM student
INNER JOIN score ON student.id = score.stu_id
WHERE score.c_name = '计算机系' AND score.grade < 95;13.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 in (select stu_id from score where c_name ='计算机' and stu_id in(select stu_id from score where c_name ='计算机'));14.将计算机考试成绩按从高到低进行排序
SELECT *
FROM score
WHERE c_name = '计算机系'
ORDER BY grade DESC;15.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;16.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.name, student.department, score.c_name, score.grade
FROM student
INNER JOIN score ON student.id = score.stu_id
WHERE student.name LIKE '张%' OR student.name LIKE '王%';17.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.name, YEAR(NOW()) - student.birth AS age, student.department, score.c_name, score.grade
FROM student
INNER JOIN score ON student.id = score.stu_id
WHERE student.address LIKE "湖南%";