Prefix best match MySQL - mysql

Question

That's my scenario.
I have 4 tables: records, providers, routing_domain, domains.
domains: id, name (something like 'example.com')
providers: id, name (something like 'TLC')
records: phone_number (varchar), provider_id (foreign key to
providers)
routing_domain: provider_id (foreign key to providers), domain_id
(foreign key to domains) and prefix (varchar).
Example of tables:
mysql> select id,name from domains;
+----+-----------------------+
| id | name |
+----+-----------------------+
| 1 | e164.arpa |
| 3 | example.com |
| 0 | localhost.localdomain |
| 4 | luigi.it |
| 2 | tim.it |
+----+-----------------------+
mysql> select id,name from providers where id in (9,10);
+----+----------+
| id | name |
+----+----------+
| 9 | TIM |
| 10 | VODAFONE |
+----+----------+
mysql> select * from routing_domain;
+----+--------+-----------+-------------+
| id | prefix | domain_id | provider_id |
+----+--------+-----------+-------------+
| 3 | 3932 | 4 | 9 |
| 1 | 39320 | 2 | 9 |
| 2 | 39321 | 3 | 10 |
+----+--------+-----------+-------------+
Now,
given a phone_number '39320xxxxxxx' with provider_id 9, i need to get
domain_id=2;
given a phone_number '39321xxxxxxx' with provider_id 9, i need to get
domain_id=4;
So, given a certain phone_number '3932xxxxxxxx' with provider_id=9, i need to do some bestmatch searching. Starting to search prefix with 6 chars, if not match, try with 5 chars and so on, until 3 chars (393).
I managed to get the correct domain from phone_number searching only from a prefix to 5 chars.
Something like:
select * FROM records r
left join routing_domain rd on rd.prefix like SUBSTRING(r.phone_number,1,5) and r.provider_id = rd.provider_id
left join providers p on p.id = rd.provider_id
left join domains d on d.id = rd.domain_id
where r.name = 'xxxxxxxxxxxx';
Any advices to do this bestmatch ?
Thank you so much!
Update
I tried with this:
select * FROM records r
left join routing_domain rd on on r.phone_number like concat(rd.prefix, '%') and r.provider_id = rd.provider_id
left join providers p on p.id = rd.provider_id
left join domains d on d.id = rd.domain_id
where r.name = 'xxxxxxxxxxxx';
Now, if i search for '39325xxxxxxx', there is a match with prefix '3932',
but if i search for '39320xxxxxxx', both prefixes will match and the search returns 2 rows.

Answer 1

One option is to have a sub-query that gives you the longest prefix matching provider_id and prefix. Something like this:
select domain_id from routing_domain
where
provider_id = 9
and '39321xxxxxxx' like concat(prefix, '%')
and length(prefix) =
( select max(length(prefix))
from routing_domain
where
provider_id = 9
and '39321xxxxxxx' like concat(prefix, '%')
)
See my fiddle here.

Answer 2

http://sqlfiddle.com/#!9/2e36df/10
SELECT r.*,
MAX(IF(rd.prefix = LEFT(r.phone_number,5),rd.prefix,
IF(rd.prefix = LEFT(r.phone_number,4),rd.prefix,
IF(rd.prefix = LEFT(r.phone_number,3),rd.prefix,''))))
FROM records r
LEFT JOIN routing_domain rd
ON r.provider_id = rd.provider_id
GROUP BY r.id
And to make it closer to your attempt:
http://sqlfiddle.com/#!9/2e36df/17
SELECT t.*, p.*, d.*
FROM (
SELECT r.*,
MAX(IF(rd.prefix = LEFT(r.phone_number,5),rd.id,
IF(rd.prefix = LEFT(r.phone_number,4),rd.id,
IF(rd.prefix = LEFT(r.phone_number,3),rd.id,'')))) as rd_id
FROM records r
LEFT JOIN routing_domain rd
ON r.provider_id = rd.provider_id
#WHERE r.phone_number = '393xxxxxxxxxx'
GROUP BY r.id
) t
LEFT JOIN routing_domain rd
ON t.rd_id = rd.id
LEFT JOIN providers p
ON p.id = rd.provider_id
LEFT JOIN domains d
ON d.id = rd.domain_id