借書還書數(shù)據(jù)庫代碼？

-- 圖書借閱數(shù)據(jù)庫設(shè)計(jì)

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-- 記錄每一本圖書借出和還回的操作

-- 書的信息

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;

-- 新建相關(guān)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 "在館"

);

-- 記錄借書和還書

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)

);

-- 給館藏圖書添加10本書

-- 存儲(chǔ)過程

DELIMITER $$$

CREATE PROCEDURE add_books( IN n INT)

BEGIN

-- 需要有多行數(shù)據(jù)放入變量，需要用 游標(biāo) cursor

-- i 局部變量

DECLARE i INT DEFAULT 1;

-- @temp全局變量

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 ;

-- 觸發(fā)器 trigger ,管理圖書被借出后，藏書和讀者信息的維護(hù)

-- 表中數(shù)據(jù)相關(guān)的操作： 增 刪 改 （查）

-- 一個(gè)表中某條記錄被修改：OLD 代表原有的那條記錄 NEW代表新的那條記錄

-- [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"在館" ) THEN

SIGNAL SQLSTATE '45000'

SET MESSAGE_TEXT = "圖書已借出！";

END IF ;

IF (v2=@READER_MAX) THEN

SIGNAL SQLSTATE '45000'

SET MESSAGE_TEXT = "讀者已經(jīng)到達(dá)最大借閱數(shù)！";

END IF ;

END $$$

DELIMITER ;

-- 書借出的數(shù)據(jù)維護(hù)

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 ;

-- 書歸還的數(shù)據(jù)維護(hù)

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="在館"

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;

-- 計(jì)算超期費(fèi)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 ;

-- 添加若干的測試數(shù)據(jù)

INSERT INTO books (name, price)

VALUES

("javascript程序設(shè)計(jì)", 19.8),

("數(shù)據(jù)庫系統(tǒng)開發(fā)", 20.8),

("mysql數(shù)據(jù)庫必知必會(huì)", 28.8);

INSERT INTO readers ( name )

VALUES

("Alice"),

("Bob"),

("Carl");

-- 測試語句

SHOW TABLES;

-- 根據(jù)書的信息添加10本館藏圖書

CALL add_books( 10) ;

SELECT * from lib_books;

-- 借書

-- 2號讀者借了2號書

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);

-- 還書

UPDATE lib_loan

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

WHERE id = 1;

-- 續(xù)借

UPDATE lib_loan

SET renew = 1

WHERE id = 4;

SELECT * FROM lib_books;

SELECT * FROM readers;

SELECT * FROM lib_loan;

java簡單的借書系統(tǒng)

HashMap的常用方法

map的存儲(chǔ)和修改方式?map.put(key, value);

map是否包含某個(gè)元素map.containsKey(key);

map某個(gè)key的value值map.get(key);

參考代碼

import?java.util.HashMap;

public?class?BookTest?{

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

static{//初始化圖書信息

map.put("三國志",?8);

map.put("紅樓夢",?0);

map.put("西游記",?15);

}

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

jieShu("水滸");

jieShu("三國志");

huanShu("三國志");

jieShu("紅樓夢");

huanShu("紅樓夢");

jieShu("紅樓夢");

}

public?static?void?jieShu(String?name){//借書

if(!map.containsKey(name)){//查詢圖書館是否有這本書

System.out.println("書籍："+name+"\t查無此書！");

return;

}

if(map.get(name)=0){//查詢圖書數(shù)量是否為0

System.out.println("書籍："+name+"\t已全部借出，請明日在來");

return;

}

map.put(name,?map.get(name)-1);

System.out.println("書籍："+name+"\t借書成功。"+"\t庫存："+map.get(name));

}

public?static?void?huanShu(String?name){//還書

if(!map.containsKey(name)){

System.out.println("查無此書");

}else{

map.put(name,?map.get(name)+1);

System.out.println("書籍："+name+"\t還書成功。"+"\t庫存："+map.get(name));

}

}

}

測試輸出

書籍：水滸 查無此書！

書籍：三國志 借書成功。 庫存：7

書籍：三國志 還書成功。 庫存：8

書籍：紅樓夢 已全部借出，請明日在來

書籍：紅樓夢 還書成功。 庫存：1

書籍：紅樓夢 借書成功。 庫存：0

java 簡單的借書還書代碼怎么寫

switch(key){

case 1:

//借書

break;

case 2:

//還書

break;

}