Tricky SQL加入查詢

我有兩個表，一個叫StudentCerts，包含一個電子郵件（主鍵）和一個證書，另一個叫CertReqs，包含一個證書和課程。表的一部分可能看起來像這樣：Tricky SQL加入查詢

 StudentCerts:         CertReqs:  
Email   Certificate    Certificate   Course 
[email protected]  Programmer   Programmer   CS 101 
[email protected]  English    Programmer   CS 202 
[email protected]   Econ     Programmer   CS 303 
[email protected]  Programmer   English    ENG 101 
             English    ENG 102 
             Econ     ECON 102 
             Econ     ECON 304 
             Art     Art 101 
             Art     Art 102 
             Journalism   J 101 
             Journalism   J 202

我試圖做的就是讓所有的特定學生不是一部分的證書。例如，[email protected]註冊了程序員和英語證書，並且我希望獲得一個SQL語句，該語句將返回CertReq中的所有證書，該特定學生未註冊。因此，對於此示例它應該返回經濟，藝術和新聞。我一直在努力爭取這一段時間，所以任何幫助將不勝感激！

來源

2012-12-07 user1875195

SELECT cr.Certificate FROM CertReqs cr 
WHERE cr.Certificate NOT IN (
    SELECT sc.Certificate FROM StudentCerts sc 
    WHERE sc.Email = '[email protected]' 
);

查詢幾乎全文的要求：「我希望所有的CertReqs，用於該學生是不是在」。

來源

2012-12-07 07:29:06

太謝謝你了！這正是我想要做的！ – user1875195

這將列出所有的學生缺乏對某一證書

SELECT DISTINCT x.* 
FROM 
    (
     SELECT a.Email, b.Certificate 
     FROM (SELECT DISTINCT Email FROM StudentCerts) a 
       CROSS JOIN 
       (SELECT DISTINCT Certificate FROM CertReqs) b 
    ) x LEFT JOIN studentCerts y 
     ON x.Email = y.Email AND 
      x.Certificate = y.Certificate 
WHERE y.Email IS NULL 
ORDER BY x.EMAIL

SQLFiddle Demo

，如果你想爲特定的電子郵件，那麼你只需要添加額外的條件

SELECT DISTINCT x.* 
FROM 
    (
     SELECT a.Email, b.Certificate 
     FROM (SELECT DISTINCT Email FROM StudentCerts) a 
       CROSS JOIN 
       (SELECT DISTINCT Certificate FROM CertReqs) b 
    ) x LEFT JOIN studentCerts y 
     ON x.Email = y.Email AND 
      x.Certificate = y.Certificate 
WHERE y.Email IS NULL AND 
     x.Email = '[email protected]' 
ORDER BY x.EMAIL

SQLFiddle Demo

來源

2012-12-07 07:30:06

SELECT Certificate FROM `CertReqs` 

WHERE Certificate NOT in(
    SELECT Certificate 
    FROM `StudentCerts` 
    WHERE Email = '[email protected]' 
)

來源

2012-12-07 07:44:57 Abhi

在比賽中有點晚，但一個簡單的LEFT JOIN解決了這個問題非常好：

SELECT DISTINCT cr.Certificate 
FROM CertReqs cr 
LEFT JOIN StudentCerts sc ON cr.Certificate = sc.Certificate AND sc.Email = '[email protected]' 
WHERE sc.Email IS NULL

來源

2012-12-07 07:51:56

SELECT DISTINCT A.* fROM 
(
SELECT DISTINCT EMAIL, CERTIFICATE fROM #StudentCerts A 
CROSS JOIN #CertReqs B) A 
LEFT JOIN #StudentCerts B ON A.EmaiL = B.EMAIL AND B.CERTIFICATES = A.Certificate 
WHERE B.EMAIL IS NULL 
ORDER BY A.EMAIL

來源

2017-07-31 12:56:06

歡迎來到Stack Overflow！儘管這段代碼可以解決這個問題，但[包括一個解釋]（// meta.stackexchange.com/questions/114762/explaining-entirely-code-based-answers）確實有助於提高您的帖子的質量。請記住，您將來會爲讀者回答問題，而這些人可能不知道您的代碼建議的原因。也請儘量不要用解釋性註釋來擠佔代碼，這會降低代碼和解釋的可讀性！ – Machavity

Tricky SQL加入查詢

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