我已经阅读了有关此主题的其他问题，但无法解决我的问题，因此发布了一个新问题。
mysql> show grants;
+----------------------------------------------------------------------------------------+
| Grants for guest@localhost |
+----------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'guest'@'localhost' |
| GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP ON `parks`.* TO 'guest'@'localhost' |
+----------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> grant SELECT, INSERT, UPDATE, DELETE, CREATE, DROP ON mamute_development.* to 'root'@'localhost';
ERROR 1044 (42000): Access denied for user 'guest'@'localhost' to database 'mamute_development'
为什么？数据库确实存在：
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mamute_development |
| mysql |
| parks |
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)
如果我尝试其他用户，我会收到同样的错误：
mysql> create user 'mamute-user'@'localhost';
Query OK, 0 rows affected (0.00 sec)
mysql> grant SELECT,INSERT,UPDATE,DELETE,CREATE,DROP on mamute_development.* to 'mamute-user'@'localhost';
ERROR 1044 (42000): Access denied for user 'guest'@'localhost' to database 'mamute_development'
如果重要，请参见下文：
$ sudo ls -al /usr/local/mysql/data/
Password:
total 379688
drwxr-x--- 19 _mysql _mysql 646 Feb 9 16:02 .
drwxr-xr-x 13 morpheus wheel 442 Oct 30 10:16 ..
-rw-r----- 1 _mysql _mysql 45643 Dec 17 08:38 my-MacBook-Pro-3170.local.err
-rw-r----- 1 _mysql _mysql 6 Nov 30 13:52 my-MacBook-Pro-3170.local.pid
-rw-r----- 1 _mysql _mysql 56 Oct 30 10:16 auto.cnf
-rw-r----- 1 _mysql _mysql 709 Jan 29 16:08 ib_buffer_pool
-rw-r----- 1 _mysql _mysql 50331648 Feb 1 09:14 ib_logfile0
-rw-r----- 1 _mysql _mysql 50331648 Nov 30 16:02 ib_logfile1
-rw-r----- 1 _mysql _mysql 79691776 Feb 1 09:14 ibdata1
-rw-r----- 1 _mysql _mysql 12582912 Feb 1 09:14 ibtmp1
drwxr-x--- 3 _mysql _mysql 102 Feb 9 16:02 mamute_development
drwxr-x--- 77 _mysql _mysql 2618 Oct 30 10:16 mysql
-rw-r----- 1 _mysql _mysql 1389508 Feb 9 16:54 mysqld.local.err
-rw-r----- 1 _mysql _mysql 3 Feb 1 09:14 mysqld.local.pid
-rw-rw---- 1 _mysql _mysql 6 Nov 30 13:52 mysqld_safe.pid
drwxr-x--- 5 _mysql _mysql 170 Oct 30 10:50 parks
drwxr-x--- 90 _mysql _mysql 3060 Oct 30 10:16 performance_schema
drwxr-x--- 108 _mysql _mysql 3672 Oct 30 10:16 sys
我删除了root用户并再次添加回来。另见下文：
$ sudo /usr/local/mysql/bin/mysql -u root
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 17101
Server version: 5.7.9 MySQL Community Server (GPL)
Copyright (c) 2000, 2015, 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.
mysql> show grants;
+------------------------------------------+
| Grants for root@localhost |
+------------------------------------------+
| GRANT USAGE ON *.* TO 'root'@'localhost' |
+------------------------------------------+
1 row in set (0.00 sec)
mysql> grant all privileges on *.* to 'root'@'localhost';
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)