From 2531b9e33fc7f17d241c468cdd77b68b6fe70d30 Mon Sep 17 00:00:00 2001
From: unknown <2112572495@qq.com>
Date: Thu, 7 Sep 2023 12:54:32 +0800
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+## 数据库设计
+
+- 表与表之间的关系：**一对多、一对一、多对多**
+
+- *关系是相互的*：一个学生，可以选多个课程；一个课程可以被多个学生选
+
+### 一对一
+
+将其中任一表中的主键放到另一个表中当外键
+
+### 一对多
+
+将一个所在表的主键，放到多的表当外键
+
+### 多对多
+
+必须第三张表，将前面两个表的主键放进来当外键
+
+------
+
+## E-R图
+
+- 概念：实体关系图，以实体、关系、属性三个基本概念概括数据的基本结构，从而描述静态数据结构的概念模式
+
+- 三要素：实体 属性 关系
+
+------
+
+## 作业
+
+```mysql
+create database StudentSystem charset utf-8;
+use StudentSystem;
+-- 学院表
+create table college(
+ c_id int primary key,
+ c_name varchar(80),
+ c_tel varchar(20)
+);
+insert into college values
+(1,'软件工程学院','167567');
+
+-- 专业表
+create table major(
+ m_id int primary key,
+ m_name varchar(20),
+ c_id int,
+ foreign key (c_id) reference college(c_id)
+);
+insert into major values
+(1,'软件开发',1),
+(2,'前端',2),
+(3,'新媒体',3);
+
+-- 班级表
+create table class(
+ s_grade varchar(10) primary key,
+ s_name varchar(20),
+ m_id int,
+ foreign key (m_id) reference major(m_id)
+);
+insert into class values
+('22级','软件1班',1),
+('22级','软件2班',1),
+('22级','软件3班',2),
+('22级','软件4班',3);
+
+-- 教室表
+create table classroom(
+ r_id int primary key,
+ r_name varchar(20),
+ r_address varchar(20),
+ courseId int,
+ foreign key (courseId) reference course(courseId)
+);
+insert into classroom values
+(1,'实训8','望云楼',1),
+(2,'实训3','望云楼',3);
+
+-- 课程
+create table course(
+ courseId int PRIMARY key,
+ courseName varchar(10),
+ s_grade varchar(10),
+ r_id int,
+ foreign key (s_id) references class(s_id),
+ foreign key (r_id) references classroom(r_id)
+);
+insert into course values
+ (1,'Java','22级',1),
+ (2,'html','22级',1),
+ (3,'MySQL','22级',2),
+ (4,'css','22级',2);
+
+-- 课程表
+create table schedule(
+ sch_id int primary key,
+ time varchar(20),
+ couseId int,
+ t_id int,
+ r_id int,
+ foreign key (couseId) references course(couseId),
+ foreign key (t_id) references teacher(t_id),
+ foreign key (r_id) references classroom(r_id)
+);
+insert into schedule values
+(1,'星期一',2,1),
+(2,'星期三',3,2);
+
+-- 教师表
+create table teacher(
+ t_id int primary key,
+ t_name varchar(10),
+ couseId int,
+ foreign key (couseId) references course(couseId)
+);
+insert into teacher values
+(1,'丘',1),
+(2,'李',2);
+
+-- 学生表
+create table student(
+ stu_id int primary key,
+ stu_name varchar(20),
+ stu_age int,
+ stu_gender varchar(10),
+ s_grade varchar(10),
+ foreign
+);
+insert into student values
+(1,'小米',16,'女','22级'),
+(2,'小花',16,'女','22级'),
+(3,'小红',16,'女','22级'),
+(4,'小明',16,'男','22级'),
+```
+
+
+
+
+
+
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--
Gitee