varchar后面的长度是指的多少空间，或者说一个长度是指一个字符或者字节，还是等于一个字

续7楼问题,解决了该bug后,又出现新的

代码  grant select on sxt.a123 to 'u_sxt'@ with grant option;

报错  1410 - You are not allowed to create a user with GRANT

老师这个注册码用不了怎么办啊

老师我这个是什么问题为啥链接失败

Tue Nov 07 04:20:51 CST 2023 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 782 milliseconds ago.  The last packet sent successfully to the server was 774 milliseconds ago.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:990)
	at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:201)
	at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:4869)
	at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1656)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1217)
	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2189)
	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2220)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2015)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:768)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:385)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:323)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:247)
	at jdbcTest.main(jdbcTest.java:22)
Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
	at sun.security.ssl.HandshakeContext.<init>(HandshakeContext.java:171)
	at sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:101)
	at sun.security.ssl.TransportContext.kickstart(TransportContext.java:238)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:394)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:373)
	at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:186)
	... 18 more

有没有一章是专门讲这些部分名称的  根本分不清哪个是哪个 看的云里雾里的

直接写关闭ResultSet、Statement、Connection，前面的关闭Connection和Statement方法可以不再写吗？

java.io.IOException;
java.io.InputStream;
java.sql.Connection;
java.sql.DriverManager;
java.sql.SQLException;
java.util.Properties;


JdbcTest2 {
    main(String[] args) IOException, ClassNotFoundException, SQLException {
        Properties prop =Properties();
        InputStream is= JdbcTest2..getClassLoader().getResourceAsStream();
        prop.load(is);
        String url = prop.getProperty();
        String name = prop.getProperty();
        String pwd = prop.getProperty();
        String drivername =prop.getProperty();

        Class.(drivername);
        Connection connection= DriverManager.(url, name, pwd);
        System..println(connection);

    }
}

老师，发下安装包，谢谢。V15200082226

老师，发一下安装包  v：z1323315121

老师，我用的mysql是以前就装好的8.0的，现在连接不了navicat

select em.LAST_NAME,em.SALARY,em.DEPARTMENT_ID from employees em

WHERE

em.SALARY IN

(SELECT

min(e.SALARY) from employees e

GROUP BY e.DEPARTMENT_ID) group by em.DEPARTMENT_ID

package com.itbaizhan;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;

/**
 * blob类型操作测试类
 */
public class BlobTest {
    /**
     * 向Movie表中插入数据
     */
    public void insertMovie(String moviename, InputStream is){
        Connection connection = null;
        PreparedStatement ps = null;

        try{
            //获取连接
            connection = jdbcUtils.getConnection();
            //获取PreparedStatement对象
            ps = connection.prepareStatement("insert into movie values(default,?,?)");
            //绑定参数
            ps.setString(1,moviename);
            ps.setBlob(2,is);
            ps.executeUpdate();

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            jdbcUtils.closeResource(ps,connection);
        }

    }

    public static void main(String[] args) throws FileNotFoundException {
        BlobTest bt = new BlobTest();
        //创建读取文件的IO流
        InputStream is = new FileInputStream(new File("d:/1.jpg"));
        bt.insertMovie("战狼",is);
    }
}

为什么我这样打出来会显示不了名字

老师，误删了root用户，要怎么处理哈？