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+## 笔记
+
+如果一个主体的属性有多个值，那这个属性就可以拆成一个新主体
+
+## 作业
+
+医生，病人，药品制表
+
+``` mysql
+
+
+/*==============================================================*/
+/* DBMS name:      MySQL 5.0                                    */
+/* Created on:     2023-09-14 08:55:14                          */
+/*==============================================================*/
+
+
+drop table if exists doctor;
+
+drop table if exists drug;
+
+drop table if exists medical;
+
+drop table if exists patients;
+
+drop table if exists prescription;
+
+/*==============================================================*/
+/* Table: doctor                                                */
+/*==============================================================*/
+create table doctor
+(
+   doc_id               int not null auto_increment,
+   doc_no               varchar(20) not null,
+   doc_name             varchar(10) not null,
+   doc_sex              varchar(5),
+   primary key (doc_id)
+);
+
+/*==============================================================*/
+/* Table: drug                                                  */
+/*==============================================================*/
+create table drug
+(
+   dro_id               int not null auto_increment,
+   dro_name             varchar(20) not null,
+   primary key (dro_id)
+);
+
+/*==============================================================*/
+/* Table: medical                                               */
+/*==============================================================*/
+create table medical
+(
+   ca_id                int not null auto_increment,
+   doc_id               int,
+   bat_no               int,
+   date                 date,
+   diagnose             varchar(50),
+   primary key (ca_id)
+);
+
+/*==============================================================*/
+/* Table: patients                                              */
+/*==============================================================*/
+create table patients
+(
+   bat_no               int not null auto_increment,
+   bat_name             varchar(10) not null,
+   bat_age              int,
+   bat_sex              varchar(5),
+   primary key (bat_no)
+);
+
+/*==============================================================*/
+/* Table: prescription                                          */
+/*==============================================================*/
+create table prescription
+(
+   dro_id               int not null,
+   ca_id                int not null,
+   bat_no               int,
+   usa                  varchar(20),
+   dosage               varchar(20),
+   primary key (dro_id, ca_id)
+);
+
+alter table medical add constraint FK_Relationship_1 foreign key (doc_id)
+      references doctor (doc_id) on delete restrict on update restrict;
+
+alter table medical add constraint FK_Relationship_2 foreign key (bat_no)
+      references patients (bat_no) on delete restrict on update restrict;
+
+alter table prescription add constraint FK_Relationship_5 foreign key (bat_no)
+      references patients (bat_no) on delete restrict on update restrict;
+
+alter table prescription add constraint FK_prescription foreign key (dro_id)
+      references drug (dro_id) on delete restrict on update restrict;
+
+alter table prescription add constraint FK_prescription2 foreign key (ca_id)
+      references medical (ca_id) on delete restrict on update restrict;
+```
+
+
+