以下SQL操作均在MYSQL上测试过
首先是表定义
1、创建student和score表
CREATE TABLE student (
id INT(10) NOT NULL UNIQUE PRIMARY KEY ,
name VARCHAR(20) NOT NULL ,
sex VARCHAR(4) ,
birth YEAR,
department VARCHAR(20) ,
address VARCHAR(50)
); 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.分别向student表和score表插入数据
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);
3.查询student表和score的所有记录
SELECT * FROM student
SELECT * FROM score
4.查询student表的第2条到第4条记录
mysql> SELECT * FROM student LIMIT 1,3;
+-----+--------+------+-------+------------+--------------+
| id | name | sex | birth | department | address |
+-----+--------+------+-------+------------+--------------+
| 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 |
+-----+--------+------+-------+------------+--------------+
5.从student表查询所有学生的学号（id）、姓名（name）和院系（department）的信息
mysql> SELECT id,name,department FROM student;
+-----+--------+------------+
| id | name | department |
+-----+--------+------------+
| 901 | 张老大 | 计算机系 |
| 902 | 张老二 | 中文系 |
| 903 | 张三 | 中文系 |
| 904 | 李四 | 英语系 |
| 905 | 王五 | 英语系 |
| 906 | 王六 | 计算机系 |
+-----+--------+------------+
6.从student表中查询计算机系和英语系的学生的信息
mysql> SELECT * FROM student WHERE department IN ('计算机系','英语系');
+-----+--------+------+-------+------------+--------------+
| id | name | sex | birth | department | address |
+-----+--------+------+-------+------------+--------------+
| 901 | 张老大 | 男 | 1985 | 计算机系 | 北京市海淀区 |
| 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 |
+-----+--------+------+-------+------------+--------------+
7.从student表中查询年龄18~22岁的学生信息
mysql> SELECT id,name,sex,2013-birth AS age,department,address
-> FROM student
-> WHERE 2013-birth BETWEEN 18 AND 22;
+-----+------+------+------+------------+--------------+
| id | name | sex | age | department | address |
+-----+------+------+------+------------+--------------+
| 905 | 王五 | 女 | 22 | 英语系 | 福建省厦门市 |
+-----+------+------+------+------------+--------------+
8.从student表中查询每个院系有多少人
SELECT department,count(department) AS nums 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) AS max_score 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 name='李四');
11.用连接的方式查询所有学生的信息和考试信息
SELECT student.id,name,sex,birth,department,address,c_name,grade
FROM student,score WHERE student.id=score.stu_id;
或者用INNER JOIN
SELECT student.id,name,sex,birth,department,address,c_name,grade
FROM student INNER JOIN score on student.id=score.stu_id;
12.计算每个学生的总成绩（SUM函数）
SELECT student.id, name,SUM(grade) FROM student INNER JOIN score on
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 student.id,student.name,student.birth,student.department,student.address
FROM student INNER JOIN score WHERE student.id = score.stu_id and c_name='计算机'
and grade < 95;
或者
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
这个操作就很有玄机了，想了两种方法，
第一种
SELECT * FROM student
WHERE id IN(
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');
因为不能用where去筛选同是'计算机'和'英语'的stu_id，所有分两步筛选
第二种，
SELECT * FROM student WHERE id IN (
SELECT stu_id FROM score WHERE c_name in ('英语','计算机')
group by stu_id having count(c_name)=2);
用having和count，简直无敌，having专门对聚类进行筛选
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 studentUNION 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, student.name,student.department,score.c_name,score.grade FROM student,score WHERE student.id = score.stu_id AND (student.name LIKE '张%' or student.name LIKE '王%');
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, student.name,student.department,score.c_name,score.grade
FROM student,score WHERE student.id = score.stu_id AND
(student.address LIKE '湖南%');
