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Question

这里我有学生拥有RollNumbers及其课程代码的示例数据.

-------------------------
    Roll      CourseCode
--------------------------
    1011       CS201
    2213       CS201
    3312       CS101
    4000       CS201
    1011       CS101
    5312       ME102
    1011       PT101
    3312      ME102

结果应该是Coursecode他们的考试日期

例如(排序不同的课程代码)

首先,我选择CS201并将该课程代码指定为日期; 将它放在一个临时表中,然后我选择了CS101并将在临时表中检查此课程代码的RollNumbers是否与临时表中其他任何其他课程代码的RollNumber匹配.

---------------------
    Code    Date
---------------------
    CS101    1
    CS201    2
    ME102    1
    PT101    3

我的代码:

• #temp3 包含所有数据(CourseCodes,RollNumbers)
• #mytemp1 (输出数据)

和cursor包含Distinct课程代码

SET @cursor = CURSOR FOR
SELECT DISTINCT coursecode
FROM #temp3
ORDER BY CourseCode

OPEN @cursor
FETCH NEXT
FROM @cursor INTO @cursorid


WHILE @@FETCH_STATUS = 0
    BEGIN 

        BEGIN
            SET @j=1
            WHILE(@j !=9999999) 
            BEGIN 

                IF( SELECT COUNT(*) FROM #temp3 WHERE CourseCode = @cursorid AND RegdNo IN (
                    SELECT  RegdNo FROM #temp3 WHERE CourseCode IN ( SELECT coursecode FROM #myTemp1 WHERE counter1 = @j)
                )) = 0
                        BEGIN
                            INSERT INTO #myTemp1 VALUES (@cursorid,@j)
                            SET @j=9999999
                        END
                ELSE   
                BEGIN
                        SET @j = @j + 1
                END 
            END
    END

FETCH NEXT
FROM @cursor INTO @cursorid
END
CLOSE @cursor
DEALLOCATE @cursor

这段代码工作正常,但花了太多时间(4110222条记录)

任何帮助,将不胜感激

Answer 1

这是一些代码。我相信您的输出有错误，CS101应该先于CS201：

DECLARE @t TABLE ( Roll INT, Code CHAR(5) )

INSERT  INTO @t
VALUES  ( 1011, 'CS201' ),
        ( 2213, 'CS201' ),
        ( 3312, 'CS101' ),
        ( 4000, 'CS201' ),
        ( 1011, 'CS101' ),
        ( 5312, 'ME102' ),
        ( 1011, 'PT101' ),
        ( 3319, 'ME102' );

WITH    cte1
          AS ( SELECT   code ,
                        ROW_NUMBER() OVER ( ORDER BY Code ) AS rn
               FROM     @t
               GROUP BY code
             ),
        cte2
          AS ( SELECT   code ,
                        rn ,
                        1 AS Date
               FROM     cte1
               WHERE    rn = 1
               UNION ALL
               SELECT   c1.code ,
                        c1.rn ,
                        CASE WHEN EXISTS ( SELECT   *
                                           FROM     @t a
                                                    JOIN @t b ON a.Roll = b.Roll
                                                    JOIN cte1 c ON c.rn < c1.rn
                                                              AND b.Code = c.code
                                           WHERE    a.code = c1.code ) THEN 1
                             ELSE 0
                        END
               FROM     cte1 c1
                        JOIN cte2 c2 ON c1.rn = c2.rn + 1
             ),
        cte3
          AS ( SELECT   Code ,
                        CASE WHEN Date = 0 THEN 1
                             ELSE SUM(Date) OVER ( ORDER BY rn )
                        END AS Date
               FROM     cte2
             )
    SELECT  * FROM    cte3

输出：

Code    Date
CS101   1
CS201   2
ME102   1
PT101   3

编辑：

cte1将返回：

code    rn
CS101   1
CS201   2
ME102   3
PT101   4

主要工作是在 中完成的cte2。它是递归公用表表达式。首先，您从以下位置获取顶部 1 行cte1：

SELECT   code ,
         rn ,
         1 AS Date
         FROM     cte1
         WHERE    rn = 1

然后递归进行：

您正在加入cte1并选择以下 rns (2, 3...)，并在第一步检查先前代码中的匹配卷cte2中是否有任何卷( )，检查先前代码中的匹配卷中是否有任何卷 ( )在第二步等中。如果存在则返回 1，否则返回 0：CS201CS101ME102CS101, CS201

code    rn  Date
CS101   1   1
CS201   2   1
ME102   3   0
PT101   4   1

Lastcte3执行以下操作：如果 Date = 0，则返回 1，否则返回前几行（包括当前行）中的日期总和。

编辑1：

由于我的理解不正确，这里再声明一下：

WITH    cte
          AS ( SELECT   code ,
                        ROW_NUMBER() OVER ( ORDER BY Code ) AS rn
               FROM     @t
               GROUP BY code
             )

  SELECT co.Code,
  DENSE_RANK() OVER(ORDER BY ISNULL(o.Code, co.Code)) AS Date
           FROM cte     co
  OUTER APPLY(SELECT TOP 1 ci.Code 
              FROM cte ci 
              WHERE ci.rn < co.rn AND 
              NOT EXISTS(SELECT * FROM @t 
                         WHERE code = ci.code AND 
                         roll IN(SELECT roll FROM @t WHERE code = co.code)) ORDER BY ci.rn) o
  ORDER BY co.rn     

输出：

Code    Date
CS101   1
CS201   2
ME102   1
PT101   2

编辑2：

这很疯狂，但是，这里的代码似乎有效：

WITH    cte
          AS ( SELECT   * ,
                        ROW_NUMBER() OVER ( PARTITION BY roll ORDER BY Code ) AS Date
               FROM     @t
             )
    SELECT  Code ,
            MAX(Date) AS Date
    FROM    cte
    GROUP BY Code