Join by part of string - mysql

Question

I have following tables:
**visitors**
+---------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------------+--------------+------+-----+---------+----------------+
| visitors_id | int(11) | NO | PRI | NULL | auto_increment |
| visitors_path | varchar(255) | NO | | | |
+---------------------+--------------+------+-----+---------+----------------+
**fedora_info**
+----------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+---------+-------+
| pid | varchar(255) | NO | PRI | | |
| owner_uid | int(11) | YES | | NULL | |
+----------------+--------------+------+-----+---------+-------+
First I looking for visitors_path that are related to specific pages by:
SELECT visitors_id, visitors_path
FROM visitors
WHERE visitors_path REGEXP '[[:<:]]fedora/repository/.*:[0-9]+$';
The above query return expected result.
now .*:[0-9]+ in above query referred to pid in second table. now I want know count of result in above query grouped by owner_uid in second table.
How can I JOIN this tables?
EDIT
sample data:
visitors
+-------------+---------------------------------+
| visitors_id | visitors_path |
+-------------+---------------------------------+
| 4574 | fedora/repository/islandora:123 |
| 4575 | fedora/repository/islandora:123 |
| 4580 | fedora/repository/islandora:321 |
| 4681 | fedora/repository/islandora:321 |
| 4682 | fedora/repository/islandora:321 |
| 4704 | fedora/repository/islandora:321 |
| 4706 | fedora/repository/islandora:456 |
| 4741 | fedora/repository/islandora:456 |
| 4743 | fedora/repository/islandora:789 |
| 4769 | fedora/repository/islandora:789 |
+-------------+---------------------------------+
fedora_info
+-----------------+-----------+
| pid | owner_uid |
+-----------------+-----------+
| islandora:123 | 1 |
| islandora:321 | 2 |
| islandora:456 | 3 |
| islandora:789 | 4 |
+-----------------+-----------+
Expected result:
+-----------------+-----------+
| count | owner_uid |
+-----------------+-----------+
| 2 | 1 |
| 4 | 2 |
| 3 | 3 |
| 2 | 4 |
| 0 | 5 |
+-----------------+-----------+

Answer 1

I suggest you to normalize your database. When inserting rows in visitors extract pid in the front end language and put it in a separate column (e.g. fi_pid). Then you can join it easily.
The following query might work for you. But it'll be little cpu intensive.
SELECT
COUNT(a.visitors_id) as `count`,
f.owner_uid
FROM (SELECT visitors_id,
visitors_path,
SUBSTRING(visitors_path, ( LENGTH(visitors_path) -
LOCATE('/', REVERSE(visitors_path)) )
+ 2) AS
pid
FROM visitors
WHERE visitors_path REGEXP '[[:<:]]fedora/repository/.*:[0-9]+$') AS `a`
JOIN fedora_info AS f
ON ( a.pid = f.pid )
GROUP BY f.owner_uid

Answer 2

Following query returns expected result, but its very slow Query took 9.6700 sec
SELECT COUNT(t2.pid), t1.owner_uid
FROM fedora_info t1
JOIN (SELECT TRIM(LEADING 'fedora/repository/' FROM visitors_path) as pid
FROM visitors
WHERE visitors_path REGEXP '[[:<:]]fedora/repository/.*:[0-9]+$') t2 ON t1.pid = t2.pid
GROUP BY t1.owner_uid