JDBC

ClassNorFoundException:com.mysql.jdbc.Driver

从官网下载connector/J，解压或者安装，构建路径

Access denied for user ‘’@‘localhost’ (using password: NO)

url路径错误。

附上2018-11-29的代码

import java.sql.*;

public class Demo {
	public static final String URL = "jdbc:mysql://localhost:3306/rank";
	public static final String USER = "root";
	public static final String PASSWORD = "156321";
	
	
	public void connect()throws Exception
	{
		Class.forName("com.mysql.jdbc.Driver");//com.mysql.cj.jdbc.Driver
		Connection conn = DriverManager.getConnection(URL,USER,PASSWORD);
		Statement stmt = conn.createStatement();
		ResultSet rs = stmt.executeQuery("SELECT * FROM ranks");
		//System.out.println("hello");
		while(rs.next())
		{
			System.out.println(rs.getString("Rank")+" "+rs.getString("Score"));
		}
	}
	public static void main(String[] args)
	{
		Demo d = new Demo();
		try{
			d.connect();
		}
		catch(Exception e)
		{
			e.printStackTrace();
			System.out.println("Something wrong!");
		}
		
	}
}

sql 代码

error 1175

set SQL_SAFE_UPDATES = 0;

where / order by

select * from ranks where day_=1 order by score DESC;
#由大到小排序，默认由小到到，
#where在order by 前

delete

delete from ranks where Name_Ball='BOO';
#delete from 表名称 where 列名称 = 值；

drop

drop database sys;
drop table rank;