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+## 笔记
+
+PowerDesigner制作ER图可以转换成数据库形式，操作形式如下：
+
+第一步：创建概念模型（类似ER图） CDM 以用户角度
+
+第二步：转换成逻辑模型 LDM 以计算机角度
+
+第三步：转换成物理 PDM 以数据角度
+
+第四步：生成DDL
+
+## ER图
+
+![8750562da5843903a5aeabd6c0b120d](https://s2.loli.net/2023/09/11/PlZvLfmqhsAMuyw.png)
+
+## sql代码
+
+```sql
+/*==============================================================*/
+/* DBMS name:      MySQL 5.0                                    */
+/* Created on:     2023/9/11 20:20:24                           */
+/*==============================================================*/
+CREATE DATABASE bookes charset utf8;
+use bookes;
+
+drop table if exists book;
+
+drop table if exists guanli;
+
+drop table if exists jie;
+
+drop table if exists librarian;
+
+drop table if exists library;
+
+drop table if exists reader;
+
+drop table if exists system;
+
+/*==============================================================*/
+/* Table: book                                                  */
+/*==============================================================*/
+create table book
+(
+   bo_id                char(10) not null,
+   sys_id               int not null,
+   bo_name              char(10) not null,
+   bo_author            char(10) not null,
+   primary key (bo_id)
+);
+
+/*==============================================================*/
+/* Table: guanli                                                */
+/*==============================================================*/
+create table guanli
+(
+   sys_id               int not null,
+   rar_id               int not null,
+   primary key (sys_id, rar_id)
+);
+
+/*==============================================================*/
+/* Table: jie                                                   */
+/*==============================================================*/
+create table jie
+(
+   bo_id                char(10) not null,
+   re_id                int not null,
+   rar_id               int,
+   primary key (bo_id, re_id)
+);
+
+/*==============================================================*/
+/* Table: librarian                                             */
+/*==============================================================*/
+create table librarian
+(
+   rar_id               int not null auto_increment,
+   lib_id               int not null,
+   rar_name             varchar(20) not null,
+   rar_sex              varchar(1) not null,
+   rar_age              int not null,
+   primary key (rar_id)
+);
+
+/*==============================================================*/
+/* Table: library                                               */
+/*==============================================================*/
+create table library
+(
+   lib_id               int not null auto_increment,
+   lib_name             varchar(10) not null,
+   lib_add              varchar(100) not null,
+   primary key (lib_id)
+);
+
+/*==============================================================*/
+/* Table: reader                                                */
+/*==============================================================*/
+create table reader
+(
+   re_id                int not null auto_increment,
+   re_name              varchar(5) not null,
+   re_age               int not null,
+   re_tel               numeric(11,0) not null,
+   primary key (re_id)
+);
+
+/*==============================================================*/
+/* Table: system                                                */
+/*==============================================================*/
+create table system
+(
+   sys_id               int not null auto_increment,
+   sys_mian             decimal(4,1) not null,
+   sys_add              varchar(100) not null,
+   sys_tel              numeric(11,0) not null,
+   primary key (sys_id)
+);
+
+alter table book add constraint FK_lay foreign key (sys_id)
+      references system (sys_id) on delete restrict on update restrict;
+
+alter table guanli add constraint FK_guanli foreign key (sys_id)
+      references system (sys_id) on delete restrict on update restrict;
+
+alter table guanli add constraint FK_guanli2 foreign key (rar_id)
+      references librarian (rar_id) on delete restrict on update restrict;
+
+alter table jie add constraint FK_jie foreign key (bo_id)
+      references book (bo_id) on delete restrict on update restrict;
+
+alter table jie add constraint FK_jie2 foreign key (re_id)
+      references reader (re_id) on delete restrict on update restrict;
+
+alter table jie add constraint FK_mate foreign key (rar_id)
+      references librarian (rar_id) on delete restrict on update restrict;
+
+alter table librarian add constraint FK_manage foreign key (lib_id)
+      references library (lib_id) on delete restrict on update restrict;
+
+
+```
+