报错：
The service already exists The current server installed: "C:\Program Files\MySQL\MySQL Server 5.7\bin\mysqld" MySQL
解决方法：
1.以管理员身份打开命令行 2.输入sc query mysql 3.输入sc delete mysql
1.以管理员身份打开命令行
2.输入sc query mysql
3.输入sc delete mysql
