1、Read uncommitted（读未提交）：可能出现脏读、不可重复读和幻读。

create table account(
	id int(36) primary key comment '主键',
      card_id varchar(16) unique comment '卡号',
      name varchar(8) not null comment '姓名',
      balance float(10,2) default 0 comment '余额'
)engine=innodb;

insert into account (id,card_id,name,balance) values (1,'6226090219290000','Tom',1000);

 

public class Boss {

	public static void main(String[] args) {
		Connection connection = null;
		Statement statement = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			String url = "jdbc:mysql://127.0.0.1:3306/test";
			connection = DriverManager.getConnection(url, "root", "root");
			connection.setAutoCommit(false);
			statement = connection.createStatement();
			String sql = "update account set balance=balance+5000 where card_id='6226090219290000'";
			statement.executeUpdate(sql);
			Thread.sleep(30000);//30秒后发现工资发错了
			connection.rollback();
			sql = "update account set balance=balance+2000 where card_id='6226090219290000'";
			statement.executeUpdate(sql);
			connection.commit();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//释放资源
		}
	}
}

public class Employye {

	public static void main(String[] args) {
		Connection connection = null;
		Statement statement = null;
		ResultSet resultSet = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			String url = "jdbc:mysql://127.0.0.1:3306/test";
			connection = DriverManager.getConnection(url, "root", "root");
			statement = connection.createStatement();
			String sql = "select balance from account where card_id='6226090219290000'";
			resultSet = statement.executeQuery(sql);
			if(resultSet.next()) {
				System.out.println(resultSet.getDouble("balance"));
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//释放资源
		}
	}
}

运行结果：6000------> 30秒阻塞后,运行结果为3000