Mysql 学校信息管理系统
1.创建数据库语句:
#创建数据库
CREATE DATABASE `schoolDB`;
USE `schoolDB`;
#创建学生表
CREATE TABLE `student`(
`sid` INT(4) AUTO_INCREMENT NOT NULL PRIMARY KEY COMMENT'学生编号',
`stuName` VARCHAR(10) NOT NULL COMMENT'学生姓名',
`age` INT(4) NOT NULL COMMENT'年龄',
`sex` INT(1) NOT NULL COMMENT'学生性别'
)ENGINE=INNODB DEFAULT CHARSET=utf8 COMMENT='学生信息表';
#创建课程表
CREATE TABLE `course`(
`cid` INT(4) PRIMARY KEY COMMENT'课程编号',
`cName` VARCHAR(50) NOT NULL COMMENT'课程名称',
`tid` INT(4) NOT NULL COMMENT'教师编号'
)ENGINE=INNODB DEFAULT CHARSET=utf8 COMMENT='课程信息表';
#创建成绩表
CREATE TABLE `score`(
`sid` INT(4) COMMENT'学生编号',
`cid` INT(4) COMMENT'课程便号',
`score` INT(4) NOT NULL COMMENT'成绩'
)ENGINE=INNODB DEFAULT CHARSET=utf8 COMMENT='成绩表';
#创建教师 表
CREATE TABLE `teacher`(
`tid` INT(4) PRIMARY KEY COMMENT'教师编号',
`teaName` VARCHAR(50) NOT NULL COMMENT'教师姓名'
)ENGINE=INNODB DEFAULT CHARSET=utf8 COMMENT='教师信息表';
#创建`score表`主键
ALTER TABLE `score` ADD CONSTRAINT `pk_score` PRIMARY KEY `score`(`sid`,`cid`);
#创建课程表外键外键关联 教师表 教师编号
ALTER TABLE `course` ADD CONSTRAINT `fk_course_teacher` FOREIGN KEY (`tid`) REFERENCES `teacher`(`tid`);
#创建成绩表外键关联 学生表 学生编号
ALTER TABLE `score` ADD CONSTRAINT `fk_score_student` FOREIGN KEY (`sid`) REFERENCES `student`(`sid`);
#创建成绩表外键关联 课程表 课程编号
ALTER TABLE `score` ADD CONSTRAINT `fk_score_course` FOREIGN KEY (`cid`) REFERENCES `course`(`cid`);
#插入学生表 数据
INSERT INTO `student` VALUES(1,'张三',16,1);
INSERT INTO `student` VALUES(2,'李三思',17,1);
INSERT INTO `student` VALUES(3,'李大齐',16,1);
INSERT INTO `student` VALUES(4,'王晓花',16,0);
INSERT INTO `student` VALUES(5,'刘得住',17,1);
INSERT INTO `student` VALUES(6,'谢谢你',16,1);
INSERT INTO `student` VALUES(7,'吴三桂',16,1);
INSERT INTO `student` VALUES(8,'桂花',16,0);
#插入教师表 数据
INSERT INTO `teacher` VALUES(101,'朱大胖');
INSERT INTO `teacher` VALUES(102,'方芳');
INSERT INTO `teacher` VALUES(103,'刘博士');
#插入课程表 数据
INSERT INTO `course` VALUES(1011,'语文',101);
INSERT INTO `course` VALUES(1012,'英语',102);
INSERT INTO `course` VALUES(1013,'数学',103);
#插入成绩表 数据
INSERT INTO `score` VALUES(1,1011,90);
INSERT INTO `score` VALUES(1,1012,70);
INSERT INTO `score` VALUES(1,1013,60);
INSERT INTO `score` VALUES(2,1011,88);
INSERT INTO `score` VALUES(2,1012,70);
INSERT INTO `score` VALUES(2,1013,70);
INSERT INTO `score` VALUES(3,1011,92);
INSERT INTO `score` VALUES(3,1012,71);
INSERT INTO `score` VALUES(3,1013,65);
INSERT INTO `score` VALUES(4,1011,99);
INSERT INTO `score` VALUES(4,1012,78);
INSERT INTO `score` VALUES(4,1013,88);
INSERT INTO `score` VALUES(5,1011,87);
INSERT INTO `score` VALUES(5,1012,79);
INSERT INTO `score` VALUES(5,1013,62);
INSERT INTO `score` VALUES(6,1011,56);
INSERT INTO `score` VALUES(6,1012,65);
INSERT INTO `score` VALUES(6,1013,75);
INSERT INTO `score` VALUES(7,1011,50);
INSERT INTO `score` VALUES(7,1012,55);
INSERT INTO `score` VALUES(7,1013,51);
INSERT INTO `score` VALUES(8,1011,95);
INSERT INTO `score` VALUES(8,1012,59);
INSERT INTO `score` VALUES(8,1013,64);
2.执行SQL查询
USE `schooldb`;
/*1.查询学过“方芳”老师所教课程的学生的学号、姓名。（假定学生所学的课程均参加了考试）。*/
#测试通过
SELECT `sid`,`stuName` FROM `student` WHERE `sid` IN(
SELECT `sid` FROM `score` WHERE `cid`=(
SELECT `cid` FROM `course` WHERE `tid`=(
SELECT `tid` FROM `teacher` WHERE `teaName`='方芳'
)
)
);
3.NOT IN取反的经典应用
/*2.查询所有课程成绩均小于60分的学生学号和姓名。*/
#改一下数据才有符合要求的数据
UPDATE `score` SET `score`=50 WHERE `sid`=7 AND `cid`=1013;
SELECT `sid`,`stuName` FROM `student` WHERE `sid` NOT IN(
SELECT `sid` FROM `score`
WHERE `score`>60
);
/*难点:步骤分析:
1.查询所有分数大于60的学生编号
2.取反,不在所有大于60分的里面的学生,就是所有成绩小于60的学生
*/
4.LIMIT不支持子查询的解决方法
/*3.查询“方芳”老师所教的“数据库”课程成绩排名在第3~6名的学生学号、姓名，
并将此记录插入新表tempScore中。（要求使用limit子句）*/
CREATE TABLE `tempScore`(
SELECT `sid`,`stuName` FROM `student` WHERE `sid` IN(
#查询方芳老师所教课程第3-6名学员的编号
SELECT `sid` FROM(
SELECT `sid` FROM `score` WHERE `cid` IN(
SELECT `cid` FROM `course` WHERE `tid`=(
SELECT `tid` FROM `teacher` WHERE `teaName`='方芳'
)
)GROUP BY `score` DESC LIMIT 2,4
)AS ta
)
);
/*难点:问题出现在mysql不支持在子查询中使用limit报错:This version of MySQL doesn’t yet support ‘LIMIT & IN/ALL/ANY/SOME subquery
解决的方法是:在limit子句外面加上一层查询"SELECT `sid` FROM()
并且给from的结果集取上别名,就不会报错
*/
4.HAVING进行分组的应用
/*4.查询有两门以上课程不及格的学生学号及其平均成绩。*/
SELECT s.sid, AVG(sc.score)
FROM `student` AS s, `score` AS sc
WHERE s.sid IN
(
SELECT `sid` FROM `score`
WHERE `score` < 60
GROUP BY `sid`
HAVING COUNT(`cid`)>= 2
)
AND s.sid=sc.sid
GROUP BY s.sid
/*用到了having 分组*/
5.创建视图
/*5.创建视图student_view，用于查询所有学生的学号、姓名、参加考试课程数、各科总成绩。*/
CREATE VIEW `student_view`
AS
SELECT s.sid,s.stuName,COUNT(c.cid),SUM(sc.score) FROM `student`AS s
INNER JOIN `score` AS sc ON sc.sid=s.sid
INNER JOIN `course` AS c ON c.cid = sc.cid
GROUP BY s.sid;
