预备知识:
数据库引擎是用于存储、处理和保护数据的核心服务。
更多关于数据库引擎知识请访问https://baike.baidu.com/item/%E6%95%B0%E6%8D%AE%E5%BA%93%E5%BC%95%E6%93%8E/1239260?fr=aladdin
设想一个情景:某位不愿意透露姓名的张三,手里有一笔钱1000块,但是手里有两张卡,想往另外一张卡上转100,通过数据库和java实现;
数据库部分代码:
create table account(
id char(36) primary key,
card_id varchar(20) unique,
name varchar(8) not null,
money float(10,2) default 0
) engine=MyISAM;
insert into account
values('6ab71673-9502-44ba-8db0-7f625f17a67d','1234567890','张三',1000);
insert into account (id,card_id,name)
values('9883a53d-9127-4a9a-bdcb-96cf87afe831','0987654321','张三’)
select * from account;
执行结果是建立了如下的表格
java代码部分
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class Test {
public static void main(String[] args) {
Connection connection = null;
Statement statement = null;
try {
//1、加载JDBC驱动程序
Class.forName("com.mysql.jdbc.Driver");
//2、获取数据库连接
String url="jdbc:mysql://127.0.0.1:3306/testjdbc";
connection = DriverManager.getConnection(url, "root", "root");
connection.setAutoCommit(false);//关闭默认自动事务提交
//3、创建Statement实例
statement = connection.createStatement();
//4、执行SQL语句
statement.addBatch("update account set money=money-100 where card_id= '1234567890'");
statement.addBatch("update account money=money+100 where card_id= '0987654321'");//此句代码部分有错误;
statement.executeBatch();//5、执行语句
connection.commit();//提交事务
} catch (Exception e) {
try {
connection.rollback();//撤销DML操作
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
}finally {
//6、关闭JDBC对象,释放资源
try {
if(statement!=null) {
statement.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
try {
if(connection!=null) {
connection.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
代码执行结果
java.sql.BatchUpdateException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '=money+100 where card_id= '0987654321'' at line 1
at com.mysql.jdbc.StatementImpl.executeBatch(StatementImpl.java:1067)
at Test.Test.main(Test.java:25)
按照我们正常的逻辑来思考,这里出现了异常,但是我们准备了处理异常的机制,理论上应该会撤销这个转账的操作口八?吓得我赶紧打开数据库see see;
张三:(口吐芬芳)我的钱钱哪去了。。。。。。(此处省略一万字)
简单点说就是MyISAM数据库引擎不支持事务,
具体介绍点击这里:https://www.cnblogs.com/kevingrace/p/5685355.html
说的较为详细