提问者:小点点

如何返回最大行基于一列在连接查询?[重复]


我有一个查询,它返回一个结果集,其中包含几个表中的一些ID。如果一个数据库获取两行或多行具有相同的QuestionID,那么我只需要具有MAX(QuestionSessionID)的一行。我怎样才能做到这一点?

我尝试了一系列不同的子查询变体,但没有成功。如何实现这一点?

查询:

SELECT AQS.QuestionSessionID, AQS.QuestionID, AQS.AnswerTextMarkerID, AQS.Correct, QG.ID AS QuestionGroupID
FROM AnswerQuestionSession AQS
JOIN QuestionSession QS ON QS.UserID = 3 
JOIN Question Q ON AQS.QuestionID = Q.ID
JOIN QuestionGroup QG ON Q.QuestionGroupID = QG.ID
WHERE AQS.AnswerTextMarkerID IN (109,110,113,114,118,121,141,146,148,152,156,157,158,172,182,183,193,194,196,197,198,211,222,227,241,242,243,257,263,271,282,283,356,396,643,644,938,939,943,944,955,956,957,958,959,970,971,972,973,978,979,1110,1111,1112,1113,1114,1115,1116,1117,1118,1120,1121,1163,1164,1165,1166,1205,1240)
AND AQS.QuestionSessionID = QS.ID
ORDER BY AQS.QuestionID, AQS.QuestionSessionID DESC;

当前结果集:

QuestionSessionID QuestionID AnswerTextMarkerID Correct QuestionGroupID
294441            112        121                1       25
22942             112        121                0       25
22942             126        141                1       39
131489            216        257                1       102
22942             222        263                1       106
22942             227        271                1       110
294435            760        955                1       5
294435            760        956                1       5

因此,在上面的示例中,我只需要其中一行的问题ID为112(具有MAX(问题SessionID)294441的行),如下所示:

期望结果集:

QuestionSessionID QuestionID AnswerTextMarkerID Correct QuestionGroupID
294441            112        121                1       25
22942             126        141                1       39
131489            216        257                1       102
22942             222        263                1       106
22942             227        271                1       110
294435            760        955                1       5
294435            760        956                1       5

更新:尝试按照评论员的建议添加另一个加入,但没有正确执行。它似乎只适用于具有多个相同问题ID的行:

SELECT AQS.QuestionSessionID, AQS.QuestionID, AQS.AnswerTextMarkerID, AQS.Correct, QG.ID AS QuestionGroupID, MaxId
FROM AnswerQuestionSession AQS
JOIN QuestionSession QS ON QS.UserID = 3 
JOIN Question Q ON AQS.QuestionID = Q.ID
JOIN QuestionGroup QG ON Q.QuestionGroupID = QG.ID
JOIN (SELECT QuestionID, MAX(QuestionSessionID) as MaxId
      FROM AnswerQuestionSession
      GROUP BY QuestionID) as mq ON mq.QuestionID = AQS.QuestionID
WHERE AQS.AnswerTextMarkerID IN (109,110,113,114,118,121,141,146,148,152,156,157,158,172,182,183,193,194,196,197,198,211,222,227,241,242,243,257,263,271,282,283,356,396,643,644,938,939,943,944,955,956,957,958,959,970,971,972,973,978,979,1110,1111,1112,1113,1114,1115,1116,1117,1118,1120,1121,1163,1164,1165,1166,1205,1240)
AND AQS.QuestionSessionID = QS.ID
/*AND AQS.QuestionSessionID = MaxId*/
ORDER BY AQS.QuestionID, AQS.QuestionSessionID DESC;
QuestionSessionID QuestionID AnswerTextMarkerID Correct QuestionGroupID MaxId
294441            112        121                1       25            294441
22942             112        121                0       25            294441
22942             126        141                1       39            293891
131489            216        257                1       102           294071
22942             222        263                1       106           294013
22942             227        271                1       110           294013
294435            760        958                1       5             294435
294435            760        959                1       5             294435
294435            760        955                1       5             294435
294435            760        956                1       5             294435
294435            760        957                1       5             294435
294435            771        970                1       241           294435
294435            771        971                1       241           294435
294435            771        972                1       241           294435
294435            776        978                1       245           294435
131489            962        1205               1       318           293592

更新2:

根据一位评论员的帮助,我对它进行了一个小小的修改,使它如期工作:

工作查询:

SELECT AQS.QuestionSessionID, AQS.QuestionID, AQS.AnswerTextMarkerID, AQS.Correct, QG.ID AS QuestionGroupID
FROM AnswerQuestionSession AQS
JOIN QuestionSession QS ON  AQS.QuestionSessionID = QS.ID 
JOIN Question Q ON AQS.QuestionID = Q.ID
JOIN QuestionGroup QG ON Q.QuestionGroupID = QG.ID
JOIN (SELECT QuestionID, MAX(QuestionSessionID) as MaxId
      FROM AnswerQuestionSession AQS2
      JOIN QuestionSession QS2 ON AQS2.QuestionSessionID = QS2.ID
      WHERE QS2.UserID = 3
      GROUP BY QuestionID) as mq ON mq.QuestionID = AQS.QuestionID
WHERE AQS.AnswerTextMarkerID IN (109,110,113,114,118,121,141,146,148,152,156,157,158,172,182,183,193,194,196,197,198,211,222,227,241,242,243,257,263,271,282,283,356,396,643,644,938,939,943,944,955,956,957,958,959,970,971,972,973,978,979,1110,1111,1112,1113,1114,1115,1116,1117,1118,1120,1121,1163,1164,1165,1166,1205,1240)
AND QS.UserID = 3 
AND AQS.QuestionSessionID = MaxId;

共1个答案

匿名用户

针对AnswerQuestionSession表上的子查询添加联接

JOIN (SELECT QuestionID, MAX(QuestionSessionID as MaxId)
      FROM AnswerQuestionSession
      GROUP BY QuestionID) as mq ON mq. QuestionID = Aqs. QuestionID

然后在WHERE子句中使用它

AND Aqs.QuestionSessionID = MaxId

这是基于更新的问题,我更改了QuestionSession上的连接,并确保在WHERE子句中使用了MaxId。

SELECT AQS.QuestionSessionID, AQS.QuestionID, AQS.AnswerTextMarkerID, AQS.Correct, QG.ID AS QuestionGroupID
FROM AnswerQuestionSession AQS
JOIN QuestionSession QS ON  AQS.QuestionSessionID = QS.ID
JOIN Question Q ON AQS.QuestionID = Q.ID
JOIN QuestionGroup QG ON Q.QuestionGroupID = QG.ID
JOIN (SELECT QuestionID, MAX(QuestionSessionID) as MaxId
      FROM AnswerQuestionSession
      GROUP BY QuestionID) as mq ON mq.QuestionID = AQS.QuestionID
WHERE AQS.AnswerTextMarkerID IN (109,110,113,114,118,121,141,146,148,152,156,157,158,172,182,183,193,194,196,197,198,211,222,227,241,242,243,257,263,271,282,283,356,396,643,644,938,939,943,944,955,956,957,958,959,970,971,972,973,978,979,1110,1111,1112,1113,1114,1115,1116,1117,1118,1120,1121,1163,1164,1165,1166,1205,1240)
AND QS.UserID = 3 
AND AQS.QuestionSessionID = MaxId
ORDER BY AQS.QuestionID, AQS.QuestionSessionID DESC;