Needed aid with complicated MySQL query - very narrow scope - mysql

Question

Here are my TABLES described and their contents:
users:
+-----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| public_key_path | varchar(100) | NO | | NULL | |
| email | varchar(50) | NO | | NULL | |
| pbox | varchar(50) | YES | UNI | NULL | |
+-----------------+--------------+------+-----+---------+----------------+
contents:
+----+-------------------+----------------------+--------+
| id | public_key_path | email | pbox |
+----+-------------------+----------------------+--------+
| 33 | /path/to/pubkey1/ | FirstUser#email.com | Pbox01 |
| 34 | /path/to/pubkey2/ | SecondUser#email.com | Pbox02 |
| 35 | /path/to/pubkey3/ | ThirdUser#email.com | Pbox03 |
+----+-------------------+----------------------+--------+
files:
+-----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| file_path | varchar(100) | NO | UNI | NULL | |
| owner_id | int(11) | NO | MUL | NULL | |
+-----------+--------------+------+-----+---------+----------------+
contents:
+-----+-----------------+----------+
| id | file_path | owner_id |
+-----+-----------------+----------+
| 104 | /path/to/file1/ | 33 |
| 105 | /path/to/file2/ | 34 |
| 106 | /path/to/file3/ | 35 |
| 107 | /path/to/file4/ | 33 |
| 108 | /path/to/file5/ | 33 |
| 109 | /path/to/file6/ | 34 |
+-----+-----------------+----------+
encrypted_symmetric_keys:
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| key_path | varchar(100) | YES | UNI | NULL | |
| file_id | int(11) | NO | MUL | NULL | |
| user_id | int(11) | NO | MUL | NULL | |
+----------+--------------+------+-----+---------+----------------+
contents:
+-----+---------------------+---------+---------+
| id | key_path | file_id | user_id |
+-----+---------------------+---------+---------+
| 106 | /path/to/key1forU1/ | 104 | 33 |
| 107 | /path/to/key2forU2/ | 105 | 34 |
| 108 | /path/to/key3forU3/ | 106 | 35 |
| 109 | /path/to/key4forU1/ | 107 | 33 |
| 110 | /path/to/key5forU1/ | 108 | 33 |
| 111 | /path/to/key6forU2/ | 109 | 34 |
| 112 | /path/to/key3forU1/ | 106 | 33 |
| 113 | /path/to/key2forU1/ | 105 | 33 |
| 114 | /path/to/key6forU1/ | 109 | 33 |
+-----+---------------------+---------+---------+
This is a newbie database for a server that stores filepaths that are encrypted with encrypted symmetric keys(ESKs).
If there is key_path /path/to/key1forU1/ that means that the key is stored for file1 for user1.
I need a query that, when given file_path (ex. "/path/to/file1/") lists all users that have access to this file.
Let me know if you need any more information, I'll provide it immediately.
I know that this is a very localized question, but I've been thinking for more than an hour about that now and I'm having horrible problems with wrapping my head around it.
Thank you very much in advance.
EDIT:
My final set of data I need is, when given
'/path/to/file1/'
would return
FirstUser#email.com
But when given for example
/path/to/file2/'
would return
FirstUser#email.com
SecondUser#email.com
because

Answer 1

I think this is what you are looking for
as this will give you all email that are using file_path = '/path/to/file6/' except the owner's email
SELECT su.email
FROM encrypted_symmetric_keys AS c
INNER JOIN users AS su ON su.id = c.user_id
INNER JOIN files AS f ON f.id = c.file_id AND f.owner_id <> c.user_id
WHERE f.file_path = '/path/to/file6/'