網上都有，大家可以試一試：
mysql> use mysql
Database changed
mysql> update user set authentication_string=password('123456') where user='root';
Query OK, 0 rows affected, 1 warning (0.06 sec)
Rows matched: 1 Changed: 0 Warnings: 1
截圖：
另外，忘記密碼怎麼修改呢？
- 打開一個cmd窗口輸入mysqld --skip-grant-tables，注意這個cmd命令窗口不要關閉
- 重新打開一個cmd窗口：（這是我是配置了環境變量的，大家按照需求進去mysql就可以（不需要輸入賬號密碼））
C:\Users\Administrator>mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.19 MySQL Community Server (GPL)
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.