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From: =?UTF-8?q?=E5=BC=A0=E8=B5=B7=E7=91=9E?= <3148024859@qq.com>
Date: Mon, 11 Sep 2023 14:21:35 +0800
Subject: [PATCH] =?UTF-8?q?=E7=AC=AC=E5=9B=9B=E6=AC=A1=E4=BD=9C=E4=B8=9A?=
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+## PowerDesigner
+
+第一步：创建概念模型（类似E-R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：转换成物理模型 PDM（以数据库角度）
+
+第四步：生成DDL 
+
+数据库设计步骤
+
+1.需求分析，了解要开发的系统的需求，明确数据和格式
+
+2.概念结构设计：将需求分析得到的抽象成概念模型，将ER图向关系模型转化
+
+3.逻辑结构设计：将概念结构转化成DBMS所支持的数据模型
+
+4.物理结构设计：将概念模型，转换成选定数据库管理系统需要的物理模型
+
+5.数据库实施：根据物理模型生成对应的DDL
+
+6.数据库维护
+
+```java
+CREATE DATABASE test22 charset utf8;
+use test22;
+
+
+/*==============================================================*/
+/* DBMS name:      MySQL 5.0                                    */
+/* Created on:     2023/9/11 10:13:52                           */
+/*==============================================================*/
+
+
+drop table if exists bookrent;
+
+drop table if exists bookreturn;
+
+drop table if exists bookse;
+
+drop table if exists uesr;
+
+/*==============================================================*/
+/* Table: bookrent                                              */
+/*==============================================================*/
+create table bookrent
+(
+   rent_id              numeric(10,0) not null,
+   book_id              int,
+   rent_date            date not null,
+   book_odate           date not null,
+   primary key (rent_id)
+);
+
+/*==============================================================*/
+/* Table: bookreturn                                            */
+/*==============================================================*/
+create table bookreturn
+(
+   re_id                numeric(10,0) not null,
+   book_id              int,
+   re_date              date not null,
+   primary key (re_id)
+);
+
+/*==============================================================*/
+/* Table: "bookse-+"                                            */
+/*==============================================================*/
+create table bookse
+(
+   book_id              int not null auto_increment,
+   user_id              numeric(10,0) not null,
+   book_name            char(5) not null,
+   book_bname           char(10) not null,
+   book_number          numeric(30,0) not null,
+   floor                numeric(10,0) not null,
+   price                int not null,
+   book_bid             char(65) not null,
+   primary key (book_id)
+);
+
+/*==============================================================*/
+/* Table: uesr                                                  */
+/*==============================================================*/
+create table uesr
+(
+   user_id              numeric(10,0) not null,
+   re_id                numeric(30,0),
+   user_name            char(10) not null,
+   password             numeric(10,0) not null,
+   primary key (user_id)
+);
+
+alter table bookrent add constraint FK_Relationship_2 foreign key (book_id)
+      references bookse (book_id) on delete restrict on update restrict;
+
+alter table bookreturn add constraint FK_Relationship_5 foreign key (book_id)
+      references bookse (book_id) on delete restrict on update restrict;
+
+alter table bookse add constraint FK_rent foreign key (user_id)
+      references uesr (user_id) on delete restrict on update restrict;
+
+alter table uesr add constraint FK_Relationship_4 foreign key (re_id)
+      references bookreturn (re_id) on delete restrict on update restrict;
+
+
+```
+
+
+
-- 
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