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@@ -0,0 +1,113 @@
+~~~MySQL
+2023.09.08
+  好像什么东西都会有一个保质期，秋刀鱼会过琪，我的idea也会过期，我在着过期的一天里，学到了什么powerdesigner，什么CDM，逻辑视图，物理视图，不错的，爱学的，待我好好琢磨一下。。。。。。
+
+
+
+
+```Mysql
+/*==============================================================*/
+/* DBMS name:      MySQL 5.0                                    */
+/* Created on:     2023/9/10 22:21:34                           */
+/*==============================================================*/
+
+
+drop table if exists Borrowing;
+
+drop table if exists UserId;
+
+drop table if exists book;
+
+drop table if exists dengji;
+
+drop table if exists jiyie;
+
+drop table if exists "return";
+
+/*==============================================================*/
+/* Table: Borrowing                                             */
+/*==============================================================*/
+create table Borrowing
+(
+   brtime               char(10) not null,
+   userid               int(10) not null auto_increment,
+   username             char(6) not null,
+   returntime           date not null,
+   bokname              char(5) not null,
+   bokid                int(10) not null auto_increment,
+   primary key (userid, bokid)
+);
+
+/*==============================================================*/
+/* Table: UserId                                                */
+/*==============================================================*/
+create table UserId
+(
+   user_id              int(10) not null auto_increment,
+   user_name            char(5) not null,
+   user_password        char(6) not null,
+   primary key (user_id)
+);
+
+/*==============================================================*/
+/* Table: book                                                  */
+/*==============================================================*/
+create table book
+(
+   bk_id                int(10) not null auto_increment,
+   bk_name              char(10) not null,
+   primary key (bk_id)
+);
+
+/*==============================================================*/
+/* Table: dengji                                                */
+/*==============================================================*/
+create table dengji
+(
+   bk_id                int not null,
+   user_id              int not null,
+   primary key (bk_id, user_id)
+);
+
+/*==============================================================*/
+/* Table: jiyie                                                 */
+/*==============================================================*/
+create table jiyie
+(
+   userid               int not null,
+   bokid                int not null,
+   user_id              int not null,
+   primary key (userid, bokid, user_id)
+);
+
+/*==============================================================*/
+/* Table: "return"                                              */
+/*==============================================================*/
+create table "return"
+(
+   userid               int not null,
+   bokid                int not null,
+   bk_id                int not null,
+   primary key (userid, bokid, bk_id)
+);
+
+alter table dengji add constraint FK_dengji foreign key (bk_id)
+      references book (bk_id) on delete restrict on update restrict;
+
+alter table dengji add constraint FK_dengji2 foreign key (user_id)
+      references UserId (user_id) on delete restrict on update restrict;
+
+alter table jiyie add constraint FK_jiyie foreign key (userid, bokid)
+      references Borrowing (userid, bokid) on delete restrict on update restrict;
+
+alter table jiyie add constraint FK_jiyie2 foreign key (user_id)
+      references UserId (user_id) on delete restrict on update restrict;
+
+alter table "return" add constraint FK_return foreign key (userid, bokid)
+      references Borrowing (userid, bokid) on delete restrict on update restrict;
+
+alter table "return" add constraint FK_return2 foreign key (bk_id)
+      references book (bk_id) on delete restrict on update restrict;
+```
+~~~
+