SQL查詢產生錯誤的計數結果

我有以下SQL查詢SQL查詢產生錯誤的計數結果

SELECT 
    DISTINCT 
    count("SiteTree_Live"."ID") 
FROM 
    "SiteTree_Live" 
    LEFT JOIN "Page_Live" ON "Page_Live"."ID" = "SiteTree_Live"."ID" 
    LEFT JOIN "TourPage_Live" ON "TourPage_Live"."ID" = "SiteTree_Live"."ID" 
    LEFT JOIN "DepartureDate" ON "DepartureDate"."TourID" = "SiteTree_Live"."ID" 
WHERE 
    ("SiteTree_Live"."Locale" = 'en_AU') 
    AND ("SiteTree_Live"."ClassName" IN ('TourPage')) 
    AND ("DepartureDate"."DepartureDate" LIKE '2012-11%')

，但它產生錯誤計數的查詢結果。假設返回的總查詢結果不應超過245，但目前返回的結果大於「4569」。

這是因爲「DepartureDate」表上的JOIN，因爲當我從「DepartureDate」表中刪除連接時，查詢返回了預期結果。

我需要對我的查詢進行哪些修改，以計算「SiteTree_Live」，「ID」和「DepartureDate」之間的Macthes「TourID」，而僅計算「SiteTree_Live」，不包括出發日期？

任何建議歡迎:)

答案

SELECT 
COUNT(DISTINCT SiteTree_Live.ID) 
FROM 
"SiteTree_Live" LEFT JOIN "Page_Live" ON "Page_Live"."ID" = "SiteTree_Live"."ID" 
LEFT JOIN "TourPage_Live" ON "TourPage_Live"."ID" = "SiteTree_Live"."ID" 
LEFT JOIN "DepartureDate" ON "DepartureDate"."TourID" = "SiteTree_Live"."ID" 
WHERE 
("SiteTree_Live"."Locale" = 'en_AU') 
AND ("SiteTree_Live"."ClassName" IN ('TourPage')) 
AND ("DepartureDate"."DepartureDate" LIKE '2013-03%')

似乎給我正確的結果。謝謝你的提示@邁克爾Berkowski

來源

2013-04-10 Lamin Barrow

你的意思'COUNT（DISTINCT SiteTree_Live.ID）'代替'DISTINCT COUNT（）'？ – 2013-04-10 18:52:05

這樣工作嗎？你所有的雙引號應該反引號。 – Barmar 2013-04-10 18:52:58

這個'DepartureDate'是一個字符類型？ – wildplasser 2013-04-10 18:54:00

小幅調整：如果DepartureDate是日期類型，那麼LIKE '2013-03%將強制它被強制轉換爲字符類型（這是一個mysql 功能）。因此，DepartureDate上的任何索引都不會使用IIRC。最好使用純範圍查詢：

SELECT 
    COUNT(DISTINCT stl.ID) 
FROM 
    SiteTree_Live stl 
LEFT JOIN 
    DepartureDate dd ON dd.TourID = stl.ID 
WHERE 
    stl.Locale = 'en_AU' 
    AND stl.ClassName = 'TourPage' 
    AND dd.DepartureDate >= '2013-03-01' 
    AND dd.DepartureDate < '2013-04-01' 
    ;

來源

2013-04-10 19:35:42 wildplasser

選擇此作爲答案，稍作修改。謝謝@wildplasser – 2013-04-11 10:05:24

做到這一點（你有一堆不需要的連接）

SELECT 
    COUNT(DISTINCT SiteTree_Live.ID) 
FROM 
    `SiteTree_Live` 
LEFT JOIN 
    `DepartureDate` ON `DepartureDate`.`TourID` = `SiteTree_Live`.`ID` 
WHERE 
    `SiteTree_Live`.`Locale` = 'en_AU' 
    AND `SiteTree_Live`.`ClassName` = 'TourPage' 
    AND `DepartureDate`.`DepartureDate` LIKE '2013-03%'

你也可以做一個GROUP BY：

SELECT 
    COUNT(SiteTree_Live.ID) 
FROM 
    `SiteTree_Live` 
LEFT JOIN 
    `DepartureDate` ON `DepartureDate`.`TourID` = `SiteTree_Live`.`ID` 
WHERE 
    `SiteTree_Live`.`Locale` = 'en_AU' 
    AND `SiteTree_Live`.`ClassName` = 'TourPage' 
    AND `DepartureDate`.`DepartureDate` LIKE '2013-03%' 
GROUP BY 
    SiteTree_Live.ID

來源

2013-04-10 19:25:32 chrislondon

SQL查詢產生錯誤的計數結果

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