0

我有一张包含考试结果的表格，如下所示：

CREATE TABLE tbl (
studentid INT,
examid INT,
score INT,
attempt INT,
percentcorrect INT
);

现在，对于每个学生，我需要提取他的最佳考试成绩（以正确率衡量），如果给定的考试以相同的最佳成绩完成了两次，则应显示最新尝试的记录。我已经用双重嵌套查询完成了它（首先选择最高百分比正确，然后从结果集中选择最大尝试，然后是其余数据），但我希望有更有效的方法来实现这一点。有任何想法吗？

编辑：我的查询：

SELECT 
    result.score
    , r2.attempt
    , r2.percentcorrect
    , r2.studentid
    , r2.examid
FROM
    tbl result JOIN
    (
        SELECT
            res.studentid
            , res.examid
            , r.percentcorrect
            , MAX(res.attempt) AS attempt
        FROM 
            tbl res JOIN
            (
                SELECT studentid, examid, MAX(percentcorrect) AS percentcorrect
                FROM tbl
                GROUP BY studentid, examid
            ) r ON r.studentid = res.studentid 
            AND r.examid = res.examid
            AND r.percentcorrect = res.percentcorrect
        GROUP BY
            res.studentid
            , res.examid
            , r.percentcorrect
        ORDER BY res.examid
      ) r2
ON r2.studentid = result.studentid
AND r2.examid = result.examid
AND r2.percentcorrect = result.percentcorrect
AND r2.attempt = result.attempt

一些样本数据：

INSERT ALL 
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(1,1,30,1,10)
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(1,1,20,2,15)
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(2,1,80,1,100)
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(2,1,80,2,90)
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(3,2,10,1,9)
INTO tbl(studentid, examid, percentcorrect, attempt, score)
VALUES(3,3,15,1,100)
SELECT * FROM DUAL; COMMIT;
4

3 回答 3

4

分析功能RANK可用于：

SELECT studentid, examid, score
FROM (
  SELECT
    studentid,
    examid,
    score,
    attempt,
    RANK() OVER (
      PARTITION BY studentid, examid
      ORDER BY score DESC, attempt DESC) AS ScoreAttemptRank
  FROM tbl
)
WHERE ScoreAttemptRank = 1

此查询将返回每个学生/每次考试的最新尝试的最佳分数。如果您只需要每个学生的最佳考试成绩而不考虑考试，请更改PARTITION BY studentid, examid为PARTITION BY studentid.

于 2013-07-23T12:36:18.760 回答
0

您可以使用命令表表达式（https://forums.oracle.com/thread/921467）和OVER（http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions137.htm）来实现结果。下面的查询是 wrt SQL Server，我们在 Oracle 中也有同样的东西。另外，为了确定同一考试的最新考试结果，我在表中有 ExamDate

;WITH    CTE_StudentResult
          AS ( SELECT   StudentId ,
                        PercentCorrect ,
                        ROW_NUMBER() OVER ( PARTITION BY StudentId ORDER BY percentcorrect DESC, ExamDate DESC ) AS RowNumber
               FROM     tbl
             )
    SELECT  StudentId ,
            PercentCorrect
    FROM    CTE_StudentResult
    WHERE   RowNumber = 1
于 2013-07-23T12:40:00.323 回答
0

试试这个

SELECT DISTINCT * FROM tbl
WHERE (studentid, percentcorrect, attempt) IN (
        SELECT   studentid, percentcorrect, MAX (attempt)
        FROM tbl
        WHERE (studentid, percentcorrect) IN (SELECT   studentid,MAX (percentcorrect)FROM tbl GROUP BY studentid)
        GROUP BY studentid, percentcorrect)
于 2013-07-23T12:49:23.540 回答