爲什麼MySQL告訴我該列不存在？

我有3個表：協會（ID，姓名）賽（ID，姓名）統計（ID，日期，associationId，typeid的，數量）爲什麼MySQL告訴我該列不存在？

我的目標是讓所有關聯的列表，並對於所有關聯，類型列表（包括數量）按照首先排序，關聯關係的總數，然後針對每個類型排序。對於這一點，我有這個疑問：

SELECT association.name AS associationName, 
     race.name AS raceName, 
     SUM(report.quantity) AS quantity, 
     subrequest.totalquantity as totalquantity 
    FROM stats report 
    JOIN association ON association.id = report.associationId 
    JOIN race ON race.id = report.raceId 
    JOIN (
     SELECT SUM(report.quantity) AS totalquantity, 
      association.id AS subId 
     FROM stats report 
     JOIN association ON association.id = report.associationId 
     WHERE date LIKE "2013-11-%" 
     GROUP BY association.id 
     ORDER BY totalquantity DESC 
    ) subrequest ON subrequest.subId = association.id 
    WHERE date LIKE "2013-11-%" 
    GROUP BY association.id, race.id 
     ORDER BY totalquantity DESC, quantity DESC

這是工作完全正常！但是現在，我想只爲每個協會提供兩種最大的類型。我嘗試這樣做：

set @num := 0, @association := ''; 
select associationName, raceName, quantity, totalquantity, 
@num := if(@association = associationName, @num + 1, 1) as row_number, 
     @association := associationName as dummy 
FROM (
    SELECT association.name AS associationName, 
     race.name AS raceName, 
     SUM(report.quantity) AS quantity, 
     subrequest.totalquantity as totalquantity 
    FROM stats report 
    JOIN association ON association.id = report.associationId 
    JOIN race ON race.id = report.raceId 
    JOIN (
     SELECT SUM(report.quantity) AS totalquantity, 
      association.id AS subId 
     FROM stats report 
     JOIN association ON association.id = report.associationId 
     WHERE date LIKE "2013-11-%" 
     GROUP BY association.id 
     ORDER BY totalquantity DESC 
    ) subrequest ON subrequest.subId = association.id 
    WHERE date LIKE "2013-11-%" 
    GROUP BY association.id, race.id 
    ORDER BY totalquantity DESC, quantity DESC 
) x 
WHERE row_number <= 2

有了這個，我有一個錯誤：＃1054 - 在「where子句」未知列「ROW_NUMBER」如果我刪除WHERE子句，它工作正常，我有結果如預期。我也有一個正確的數字列row_number。

我必須這樣做，使其工作：

set @num := 0, @association := ''; 
select associationName, raceName, quantity, totalquantity 
FROM (
    select associationName, raceName, quantity, totalquantity, 
    @num := if(@association = associationName, @num + 1, 1) as row_number, 
      @association := associationName as dummy 
    FROM (
     SELECT association.name AS associationName, 
      race.name AS raceName, 
      SUM(report.quantity) AS quantity, 
      subrequest.totalquantity as totalquantity 
     FROM association_race_report report 
     JOIN association ON association.id = report.associationId 
     JOIN race ON race.id = report.raceId 
     JOIN (
      SELECT SUM(report.quantity) AS totalquantity, 
       association.id AS subId 
      FROM association_race_report report 
      JOIN association ON association.id = report.associationId 
      WHERE date LIKE "2013-11-%" 
      GROUP BY association.id 
      ORDER BY totalquantity DESC 
     ) subrequest ON subrequest.subId = association.id 
     WHERE date LIKE "2013-11-%" 
     GROUP BY association.id, race.id 
     ORDER BY totalquantity DESC, quantity DESC 
    ) x 
)y 
WHERE row_number <= 2

這工作得很好！但我不明白爲什麼我需要添加另一個級別的請求來使WHERE子句工作？這真讓我很煩，因爲我添加了無用的查詢級別。有沒有辦法讓它工作？爲什麼MySQL提出這個錯誤？

謝謝！

來源

2013-11-21 user3017110

我終於找到了解決方案！如果（@association = associationName，@num + 1，1）<= 2，我只需要將WHERE row_number <= 2替換爲WHERE – user3017110

MySQL不喜歡列引用，因爲它在查詢的選擇部分被定義 - 它在連接和where子句中都沒有用。

這些解決方案，我看到你自己發現的，都是用定義它的表達式替換別名，或者創建一箇中間子查詢以避免重寫整個事物。（查詢優化器會正常刪除中間查詢。）

來源

2013-11-25 13:21:19

爲什麼MySQL告訴我該列不存在？

回答

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