sql嵌套連接內部和左連接

Question

嗨，我想使用帶有跟蹤列表的MySQL過濾日志。

每個日志都屬於一台服務器，

每個跟蹤都屬於服務器，並且具有0..N個模式

每個模式都屬於一個跟蹤

我有3張桌子：

logs     : |  id  |      ip     | url     | server_id | ...
tracking : |  id  | server_id   | name    | other fields...
pattern  : |  id  | tracking_id | pattern |

我想計算與特定服務器的跟蹤匹配的日志，我的問題是我的查詢混淆了有模式和無模式的跟蹤。

SQL小提琴： 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

我的問題是在第二次INNER JOIN patterns as pt ON ，如果我將INNER JOIN patterns as pt ON我將獲得正確的結果，但僅在具有某些模式的跟蹤上才能獲得結果;如果我將LEFT JOIN patterns as pt ON我將獲得所有跟蹤，但計數錯誤（ SELECT COUNT(DISTINCT logs.ip) FROM logs獲取SELECT COUNT(DISTINCT logs.ip) FROM logs的結果

編輯我可以在跟蹤字段中獲得正確的結果，該字段指示跟蹤是否具有模式和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
)

但我想有一種方法可以不使用Union ...

Answer 1

您可以添加一個有條件的內部count ，因此我認為以下內容可以滿足您的需求：

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

編輯：

這將返回您想要的：

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;

您的SQL Fiddle具有附加條件lg.size > tr.size ，該條件lg.size > tr.size原始問題中。