周测

CREATE  TABLE  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)
);
CREATE  TABLE  score(
id        INT(10) PRIMARY KEY AUTO_INCREMENT,
  stu_id    INT(10) NOT NULL,
  c_name    VARCHAR(20),
  grade     INT(10)
);
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);




//查询student表的所有记录
SELECT * FROM student;
//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 AS '学号',name AS '姓名',department AS '院系' FROM student;
//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 student WHERE department IN ('计算机系','英语系');
//从student表中查询年龄28~32岁的学生信息（用 BETWEEN AND）
SELECT * FROM student WHERE YEAR(NOW())-birth BETWEEN 28 AND 32;
//从student表中查询每个院系有多少人
SELECT department AS '院系',COUNT(*) AS '该院人数' FROM student GROUP BY department;
//从score表中查询每个科目的最高分
SELECT c_name AS '科目名称',MAX(grade) AS '最高分' FROM score GROUP BY c_name;
//查询李四的考试科目（c_name）和考试成绩（grade）
SELECT s.name AS '姓名',c.c_name AS '课程名称',c.grade AS '课程分数' 
FROM score AS c LEFT JOIN student AS s ON c.stu_id = s.id
WHERE s.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 c LEFT JOIN student AS s ON c.stu_id = s.id;
//计算每个学生的总成绩
SELECT s.name AS '姓名',SUM(c.grade) AS '总成绩' FROM score AS c
LEFT JOIN student AS s ON c.stu_id = s.id GROUP BY s.name;
//计算每个考试科目的平均成绩
SELECT c_name AS '课程名称',AVG(grade) AS '平均成绩' FROM score GROUP BY c_name;
//查询计算机成绩低于95的学生信息
SELECT s.* FROM score AS c LEFT JOIN student AS s ON c.stu_id = s.id
WHERE c.c_name = '计算机' AND c.grade < 95;
//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' OR c_name = '英语' GROUP BY stu_id HAVING COUNT(*) = 2);
//将计算机考试成绩按从高到低进行排序
SELECT grade AS '计算机考试成绩' 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 AS '学号' FROM student
UNION
SELECT DISTINCT stu_id AS '学号' 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 s.name AS '姓名',s.department AS '院系',c.c_name AS '考试科目',c.grade AS '成绩'
FROM score AS c LEFT JOIN student AS s ON c.stu_id = s.id
WHERE s.name LIKE '张%' OR s.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 s.name AS '姓名',YEAR(NOW())-s.birth AS '年龄',s.department AS '院系',c.c_name AS '考试科目',c.grade AS '成绩'
FROM score AS c LEFT JOIN student AS s ON c.stu_id = s.id
WHERE s.address LIKE '湖南%';