借书还书数据库代码？

-- 图书借阅数据库设计

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-- 记录每一本图书借出和还回的操作

-- 书的信息

DROP DATABASE IF EXISTS db_lib;

CREATE DATABASE db_lib;

use db_lib

SET @READER_MAX = 10;

SET @EVERY_DAY_FEE=0.1;

SELECT 10 INTO @temp;

-- 新建相关的表

CREATE TABLE books (

id INT PRIMARY KEY AUTO_INCREMENT,

name CHAR(255) NOT NULL,

price DECIMAL(8,2) DEFAULT 0

);

CREATE TABLE readers (

id INT PRIMARY KEY AUTO_INCREMENT,

name CHAR(255) NOT NULL,

borrowed INT DEFAULT 0

);

CREATE TABLE lib_books (

id INT PRIMARY KEY AUTO_INCREMENT,

info INT,

FOREIGN KEY(info) REFERENCES books(id),

stat CHAR(10) NOT NULL DEFAULT "在馆"

);

-- 记录借书和还书

CREATE TABLE lib_loan (

id INT AUTO_INCREMENT,

who INT,

which INT,

check_out DATETIME NOT NULL DEFAULT NOW(),

check_in DATETIME DEFAULT NULL,

renew BOOLEAN NOT NULL DEFAULT 0,

latest DATE NOT NULL,

fee DECIMAL(8,2) DEFAULT NULL,

PRIMARY KEY(id),

FOREIGN KEY(who) REFERENCES readers(id),

FOREIGN KEY(which) REFERENCES lib_books(id)

);

-- 给馆藏图书添加10本书

-- 存储过程

DELIMITER $$$

CREATE PROCEDURE add_books( IN n INT)

BEGIN

-- 需要有多行数据放入变量，需要用 游标 cursor

-- i 局部变量

DECLARE i INT DEFAULT 1;

-- @temp全局变量

SELECT COUNT(*) INTO @temp

FROM books;

WHILE i=n DO

INSERT INTO lib_books (info) VALUES ( FLOOR(RAND()*@temp)+1 );

SET i = i+1;

END WHILE;

END $$$

DELIMITER ;

-- 触发器 trigger ,管理图书被借出后，藏书和读者信息的维护

-- 表中数据相关的操作： 增 删 改 （查）

-- 一个表中某条记录被修改：OLD 代表原有的那条记录 NEW代表新的那条记录

-- [BEFORE | AFTER] [INSERT | UPDATE | (DELETE) ]

DELIMITER $$$

CREATE TRIGGER before_insert_loan

BEFORE INSERT ON lib_loan

FOR EACH ROW

BEGIN

-- OLD NEW 已知

DECLARE v1 CHAR(100);

DECLARE v2 INT;

SET NEW.latest =DATE_ADD(NEW.check_out,INTERVAL 1 month);

-- 只能修改NEW

SELECT stat INTO v1

FROM lib_books

WHERE id=NEW.which;

SELECT borrowed INTO v2

FROM readers

WHERE id=NEW.who;

IF ( v1"在馆" ) THEN

SIGNAL SQLSTATE '45000'

SET MESSAGE_TEXT = "图书已借出！";

END IF ;

IF (v2=@READER_MAX) THEN

SIGNAL SQLSTATE '45000'

SET MESSAGE_TEXT = "读者已经到达最大借阅数！";

END IF ;

END $$$

DELIMITER ;

-- 书借出的数据维护

DELIMITER $$$

CREATE TRIGGER after_insert_loan

AFTER INSERT ON lib_loan

FOR EACH ROW

BEGIN

UPDATE lib_books

SET stat = "已借出"

WHERE id = NEW.which ;

UPDATE readers

SET borrowed = borrowed + 1

WHERE id = NEW.who;

END $$$

DELIMITER ;

-- 书归还的数据维护

DELIMITER $$$

CREATE TRIGGER after_update_loan

AFTER UPDATE ON lib_loan

FOR EACH ROW

BEGIN

IF(OLD.check_in is NULL AND NEW.check_in is NOT NULL) THEN

UPDATE lib_books

SET stat="在馆"

WHERE id= NEW.which;

UPDATE readers

SET borrowed=borrowed -1

WHERE id=OLD.who;

END IF;

END $$$

DELIMITER ;

DELIMITER $$$

CREATE TRIGGER before_update_loan

BEFORE UPDATE ON lib_loan

FOR EACH ROW

BEGIN

DECLARE x INT;

IF(OLD.renew=0 AND NEW.renew=1 ) THEN

SET NEW.latest=DATE_ADD(OLD.latest,INTERVAL 1 month);

END IF;

-- 计算超期费用

IF(OLD.check_in is NULL AND NEW.check_in is NOT NULL) THEN

SET x=DATEDIFF(NEW.check_in,NEW.latest);

IF(x=0 )THEN

SET NEW.fee =0 ;

ELSE

SET NEW.fee=@EVERY_DAY_FEE*x;

END IF;

END IF;

END $$$

DELIMITER ;

-- 添加若干的测试数据

INSERT INTO books (name, price)

VALUES

("javascript程序设计", 19.8),

("数据库系统开发", 20.8),

("mysql数据库必知必会", 28.8);

INSERT INTO readers ( name )

VALUES

("Alice"),

("Bob"),

("Carl");

-- 测试语句

SHOW TABLES;

-- 根据书的信息添加10本馆藏图书

CALL add_books( 10) ;

SELECT * from lib_books;

-- 借书

-- 2号读者借了2号书

INSERT INTO lib_loan (who , which ) VALUES (2,2);

INSERT INTO lib_loan (who , which ) VALUES (2,3);

INSERT INTO lib_loan (who , which ) VALUES (2,4);

INSERT INTO lib_loan (who , which ) VALUES (1,2);

INSERT INTO lib_loan (who , which ) VALUES (1,6);

INSERT INTO lib_loan (who , which ) VALUES (2,1);

INSERT INTO lib_loan (who , which ) VALUES (1,1);

-- 还书

UPDATE lib_loan

SET check_in='2022-12-15 12:00:00'

WHERE id = 1;

-- 续借

UPDATE lib_loan

SET renew = 1

WHERE id = 4;

SELECT * FROM lib_books;

SELECT * FROM readers;

SELECT * FROM lib_loan;

java简单的借书系统

HashMap的常用方法

map的存储和修改方式 map.put(key, value);

map是否包含某个元素map.containsKey(key);

map某个key的value值map.get(key);

参考代码

import java.util.HashMap;

public class BookTest {

static HashMapString, Integer map=new HashMapString, Integer();

static{//初始化图书信息

map.put("三国志", 8);

map.put("红楼梦", 0);

map.put("西游记", 15);

}

public static void main(String[] args) {//main方法

jieShu("水浒");

jieShu("三国志");

huanShu("三国志");

jieShu("红楼梦");

huanShu("红楼梦");

jieShu("红楼梦");

}

public static void jieShu(String name){//借书

if(!map.containsKey(name)){//查询图书馆是否有这本书

System.out.println("书籍："+name+"\t查无此书！");

return;

}

if(map.get(name)=0){//查询图书数量是否为0

System.out.println("书籍："+name+"\t已全部借出，请明日在来");

return;

}

map.put(name, map.get(name)-1);

System.out.println("书籍："+name+"\t借书成功。"+"\t库存："+map.get(name));

}

public static void huanShu(String name){//还书

if(!map.containsKey(name)){

System.out.println("查无此书");

}else{

map.put(name, map.get(name)+1);

System.out.println("书籍："+name+"\t还书成功。"+"\t库存："+map.get(name));

}

}

}

测试输出

书籍：水浒 查无此书！

书籍：三国志 借书成功。 库存：7

书籍：三国志 还书成功。 库存：8

书籍：红楼梦 已全部借出，请明日在来

书籍：红楼梦 还书成功。 库存：1

书籍：红楼梦 借书成功。 库存：0

java 简单的借书还书代码怎么写

switch(key){

case 1:

//借书

break;

case 2:

//还书

break;

}

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