Rails中的復雜MySQL查詢

Question

我們提供有關NCAA運動員以及這些運動員在哪里上高中的信息。 我們想按參加過該高中的NCAA運動員的數量來對高中排名。

我們有players ， teams ， team_histories ， accounts和player_to_team_histories 。 account代表學校（名稱，位置，類型（大學，高中））， team描述account中的特定球隊（男子足球，女子排球）， team_history代表特定team一年（2012年男子足球）隊），一個player代表了運動員的傳記信息（在那里長大，他們出席了高中，他們的名字），一個player_to_team_history代表player在team_history （統計年度，尺寸，重量，位置）。

我已經計算出以下MySQL查詢，以提取特定學院每所中學的運動員人數排名。 我將從最里面的語句開始分解下面的查詢：

SELECT WrappedQuery.rank FROM
(SELECT 
    @rownum := @rownum+1 AS rank, q.Name, q.id
FROM    
    (SELECT @rownum := 0) counter, 
    (SELECT 
        Accounts.id, Accounts.Name, COUNT(Accounts.Name) AS count
    FROM
        player_to_team_histories
    INNER JOIN team_histories ON team_histories.id = player_to_team_histories.team_history_id
    INNER JOIN teams ON teams.id = team_histories.team_id
    INNER JOIN accounts ON accounts.id = teams.account_id
    WHERE
        accounts.AccountTypeId = 1 AND player_id IN (SELECT 
            player_id
        FROM
            player_to_team_histories
        WHERE
            player_to_team_histories.not_valid IS NULL AND team_history_id = (SELECT 
                team_history_id
            FROM
                player_to_team_histories
            INNER JOIN team_histories ON team_histories.id = player_to_team_histories.team_history_id
            WHERE
                player_to_team_histories.id = 574651))
    GROUP BY Accounts.Name
    ORDER BY count DESC) q) WrappedQuery
WHERE WrappedQuery.id = 7661

團隊歷史記錄ID

SELECT 
    team_history_id
FROM
    player_to_team_histories
        INNER JOIN
    team_histories ON team_histories.id = player_to_team_histories.team_history_id
WHERE
    player_to_team_histories.id = 574651

這將提取我們感興趣的大學隊的team_history_id ，這使我們能夠獲取所選球員的隊友（由player_to_team_history.id = 574651標識），因為所有隊友都具有相同的team_history_id。

隊友

SELECT 
    player_id
FROM
    player_to_team_histories
WHERE
    player_to_team_histories.not_valid IS NULL AND team_history_id = (SELECT 
        team_history_id
    FROM
        player_to_team_histories
            INNER JOIN
        team_histories ON team_histories.id = player_to_team_histories.team_history_id
    WHERE
        player_to_team_histories.id = 574651)

我們使用該team_history_id獲取所選玩家的所有隊友。 然后，我們使用玩家找到他們的高中。

高中隊

SELECT 
    Accounts.id, Accounts.Name, COUNT(Accounts.Name) AS count
FROM
    player_to_team_histories
        INNER JOIN
    team_histories ON team_histories.id = player_to_team_histories.team_history_id
        INNER JOIN
    teams ON teams.id = team_histories.team_id
        INNER JOIN
    accounts ON accounts.id = teams.account_id
WHERE
    accounts.AccountTypeId = 1 AND player_id IN (SELECT 
        player_id
    FROM
        player_to_team_histories
    WHERE
        player_to_team_histories.not_valid IS NULL AND team_history_id = (SELECT 
            team_history_id
        FROM
            player_to_team_histories
                INNER JOIN
            team_histories ON team_histories.id = player_to_team_histories.team_history_id
        WHERE
            player_to_team_histories.id = 574651))
GROUP BY Accounts.Name
ORDER BY count DESC

通過獲取與我們感興趣的所有球員相關的與高中相關的player_to_team_history （ player_to_team_history accounts.AccountTypeId = 1 ），我們可以找出隊友參加過的高中，並按accounts.id對它們進行分組，然后按每個組的數量進行排序，從而為我們提供了一個排序列表，列出了在大學名冊中哪些高中球員最多。

排行

SELECT WrappedQuery.rank FROM
(SELECT 
    @rownum := @rownum+1 AS rank, q.Name, q.id
FROM    
    (SELECT @rownum := 0) counter, 
    (SELECT 
        Accounts.id, Accounts.Name, COUNT(Accounts.Name) AS count
    FROM
        player_to_team_histories
    INNER JOIN team_histories ON team_histories.id = player_to_team_histories.team_history_id
    INNER JOIN teams ON teams.id = team_histories.team_id
    INNER JOIN accounts ON accounts.id = teams.account_id
    WHERE
        accounts.AccountTypeId = 1 AND player_id IN (SELECT 
            player_id
        FROM
            player_to_team_histories
        WHERE
            player_to_team_histories.not_valid IS NULL AND team_history_id = (SELECT 
                team_history_id
            FROM
                player_to_team_histories
            INNER JOIN team_histories ON team_histories.id = player_to_team_histories.team_history_id
            WHERE
                player_to_team_histories.id = 574651))
    GROUP BY Accounts.Name
    ORDER BY count DESC) q) WrappedQuery
WHERE WrappedQuery.id = 7661

我們通過對排名的每一行編號並抓住感興趣的行來結束。在這種情況下，我們對AccountId為7661的高中感興趣。這是所選玩家參加的高中，這將告訴我們在所有為當前大學名單做出貢獻的高中中，我們都是我們所選擇的高中排名的球員。

如何在Rails中做到這一點

這是我迷路的地方。 我將如何處理這些嵌套的聯接/子查詢和結果排名？

我完全理解，這可能是解決此問題的可怕方法。 將其分解為多個查詢並將所有內容重新組合到Rails中會更好嗎？

select_by_sql執行select_by_sql ，還有什么地方可以使用Rails select_by_sql此操作？

版本

Rails 3.2.1
Ruby 1.9.2 

Answer 1

這可以使用AREL完成，但是需要大量挖掘。 但是我過去使子查詢更容易使用的是使用squeel

“ Squeel通過使位於ActiveRecord下的ARel令人敬畏，可以​​使用更少的字符串和更多的Ruby編寫ActiveRecord查詢。”

Answer 2

盡管這不能完全回答您的問題，但我建議您嘗試一下以解決您的問題。

進行現有的SQL查詢並使用SQL模板gem。

你可以嘗試像Yayql這是基於Yesql ，但任何文本或SQL模板引擎都行。