sql nested join inner and left join - mysql

Question

Hi I want to filter logs using MySQL with a list of trackings.
Every log belongs to a server,
Every tracking belongs to a server and have 0..N patterns
Every pattern belongs to a tracking
I have 3 tables :
logs : | id | ip | url | server_id | ...
tracking : | id | server_id | name | other fields...
pattern : | id | tracking_id | pattern |
I want to count logs that match tracking for a specific server my problem is that my query mix up tracking that have pattern and those that don't.
SQL Fiddle : http://sqlfiddle.com/#!2/f11b1/2
SELECT COUNT(DISTINCT logs.ip), tr.name
FROM `logs`
INNER JOIN `trackings` as tr ON
( tr.server_id = logs.server_id )
AND -- OTHER conditions between log and tracking
LEFT JOIN `patterns` as pt ON
( pt.tracking_id = tr.id )
AND (logs.url LIKE pt.pattern )
GROUP BY tr.id
My problem is on the second join, if I use INNER JOIN patterns as pt ON I get correct results but only on trackings that have some patterns,
If I use LEFT JOIN patterns as pt ON I get all tracking but with a false count (I get the result of SELECT COUNT(DISTINCT logs.ip) FROM logs )
EDIT
I Can get the correct result with a field in tracking that indicates if the tracking has patterns and a UNION :
(
SELECT COUNT(DISTINCT lg.ip), tr.name
FROM `logs` as lg
INNER JOIN `trackings` as tr ON
( tr.server_id = lg.server_id )
AND (tr.hasPatterns = 1)
AND -- Other conditions
INNER JOIN `patterns` as pt ON
( pt.tracking_id = tr.id )
AND (lg.url LIKE pt.pattern )
WHERE
GROUP BY tr.id
)
UNION
(
SELECT COUNT(DISTINCT lg.ip), tr.name
FROM `logs` as lg
INNER JOIN `trackings` as tr ON
( tr.server_id = lg.server_id )
AND (tr.hasPatterns = 0)
WHERE
GROUP BY tr.id, lg.date
)
But I guess there is a way to do that without using Union...

Answer 1

You can put a conditional inside count, so I think the following does what you want:
SELECT COUNT(DISTINCT (case when tr.hasPatterns = 1 and pt.tracking_id is not null
then lg.ip
when tr.hasPatterns = 0
then lg.ip
end)), tr.name
FROM `logs` as lg
INNER JOIN `trackings` as tr ON
( tr.server_id = lg.server_id )
AND -- Other conditions
LEFT JOIN `patterns` as pt ON
( pt.tracking_id = tr.id )
AND (lg.url LIKE pt.pattern )
WHERE
GROUP BY tr.id
EDIT:
This is returning what you want:
SELECT COUNT(DISTINCT (case when tr.size = 0 and pt.tracking_id is not null
then lg.ip
when tr.size > 0 and lg.size > tr.size
then lg.ip
end)), tr.name
FROM `logs` as lg
INNER JOIN `trackings` as tr ON
( tr.server_id = lg.server_id )
LEFT JOIN `patterns` as pt ON
( pt.tracking_id = tr.id )
AND (lg.url LIKE pt.pattern )
GROUP BY tr.id;
Your SQL Fiddle has the additional condition lg.size > tr.size which is not in the original question.