sql嵌套连接内部和左连接

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.