MySQL远程访问配置与常见问题解决指南

# 本地登录（默认走 localhost）
mysql -u root -p
# 指定 IP 登录（走网络连接）
mysql -h 192.168.1.100 -u root -p
# 指定端口
mysql -h 192.168.1.100 -P 3306 -u root -p
# 退出
exit;
-- 或
quit;

-- 查看所有用户
SELECT User, Host, plugin FROM mysql.user;
-- 创建本地用户
CREATE USER 'alice'@'localhost' IDENTIFIED BY '密码';
-- 创建远程用户（允许任意 IP）
CREATE USER 'bob'@'%' IDENTIFIED BY '密码';
-- 创建远程用户（只允许特定 IP）
CREATE USER 'charlie'@'192.168.1.50' IDENTIFIED BY '密码';
-- 修改密码
ALTER USER 'bob'@'%' IDENTIFIED BY '新密码';
-- 删除用户
DROP USER 'bob'@'%';
-- 刷新权限（修改后必须执行）
FLUSH PRIVILEGES;

-- 授予所有权限
GRANT ALL PRIVILEGES ON *.* TO 'bob'@'%';

-- 授予特定数据库权限
GRANT ALL PRIVILEGES ON mydb.* TO 'bob'@'%';

-- 授予只读权限
GRANT SELECT ON mydb.* TO 'readonly'@'%';

-- 撤销权限
REVOKE ALL PRIVILEGES ON *.* FROM 'bob'@'%';

-- 查看用户权限
SHOW GRANTS FOR 'bob'@'%';

-- 创建数据库
CREATE DATABASE mydb CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- 查看所有数据库
SHOW DATABASES;

-- 切换数据库
USE mydb;

-- 创建表
CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- 查看表结构
DESC users;
-- 或
SHOW CREATE TABLE users;

-- 插入数据
INSERT INTO users (name, email) VALUES ('张三', 'zhangsan@example.com');

-- 查询
SELECT * FROM users WHERE name LIKE '%张%';

-- 更新
UPDATE users SET email = 'new@example.com' WHERE id = 1;

-- 删除
DELETE FROM users WHERE id = 1;

# 启动
sudo systemctl start mysql
# 停止
sudo systemctl stop mysql
# 重启
sudo systemctl restart mysql
# 查看状态
sudo systemctl status mysql

# 允许所有网卡监听（默认 127.0.0.1 只监听本地）
bind-address = 0.0.0.0
# 或注释掉该行
# bind-address = 127.0.0.1

sudo systemctl restart mysql

# UFW (Ubuntu/Debian)
sudo ufw allow 3306/tcp
# firewalld (CentOS/RHEL)
sudo firewall-cmd --permanent --add-port=3306/tcp
sudo firewall-cmd --reload
# 云服务器还需在安全组中放行 3306 端口

-- 创建远程专用用户（推荐）
CREATE USER 'remote_user'@'%' IDENTIFIED BY '强密码';
GRANT ALL PRIVILEGES ON mydb.* TO 'remote_user'@'%';
FLUSH PRIVILEGES;

mysql_real_connect failed: Host '10.136.26.183' is blocked because of many connection errors;
unblock with 'mysqladmin flush-hosts'

# 服务端执行，清空黑名单
mysqladmin flush-hosts

FLUSH HOSTS;

mysql_real_connect failed: Authentication plugin 'caching_sha2_password' cannot be loaded: 找不到指定的模块。

ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'10.136.11.246'

SELECT User, Host FROM mysql.user;

+------+-----------+
| User | Host      |
+------+-----------+
| root | %         |
| root | localhost |
+------+-----------+

SELECT User, Host, plugin FROM mysql.user WHERE User = 'root';

-- 修改已存在的 'root'@'%' 用户
ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY '你的密码';
FLUSH PRIVILEGES;

SELECT User, Host, plugin FROM mysql.user WHERE User = 'root';

FLUSH HOSTS;

#include <mysql.h>
MYSQL* conn = mysql_init(nullptr);
if (!mysql_real_connect(conn, 
                        "10.136.11.246",  // 服务器 IP
                        "root",           // 用户名
                        "你的密码",        // 密码
                        "数据库名",        // 数据库
                        3306,             // 端口
                        nullptr, 0)) {
    printf("连接失败: %s\n", mysql_error(conn));
} else {
    printf("连接成功！\n");
}
mysql_close(conn);

-- 改单个用户
ALTER USER 'user'@'%' IDENTIFIED WITH mysql_native_password BY '密码';

-- 或改全局默认（my.cnf）
[mysqld]
default_authentication_plugin = mysql_native_password

# 本地建立隧道，把远程 3306 映射到本地 3307
ssh -L 3307:localhost:3306 user@服务器IP
# 然后 C++ 连接本地 3307，实际走的是加密 SSH
mysql_real_connect(conn, "127.0.0.1", "root", ..., 3307, ...);

-- 查看当前连接
SHOW PROCESSLIST;

-- 查看连接错误阈值
SHOW VARIABLES LIKE 'max_connect_errors';

-- 修改阈值（临时）
SET GLOBAL max_connect_errors = 1000;

-- 查看用户认证方式
SELECT User, Host, plugin, authentication_string FROM mysql.user;

-- 查看被拉黑的 IP（performance_schema 需开启）
SELECT * FROM performance_schema.host_cache WHERE SUM_CONNECT_ERRORS > 0;