MYSQL* mysql = new MYSQL();
//MYSQL mysql;//占用的是栈上的内存 数据库放在线程上，而不是主函数中
MYSQL* pDB = mysql_init(mysql);
//连接库
pDB = mysql_real_connect(pDB, "localhost", "user", "password", "mysql", 3306, NULL, 0);
//创建用户
sql = "CREATE USER 'hello'@'localhost' IDENTIFIED BY '123456'";
mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
//用户提权
sql = "GRANT ALL ON *.* TO 'hello'@'localhost'";
mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size())
//用户降权
sql = "REVOKE ALL ON *.* FROM 'hello'@'localhost'";
mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());