Question

我一直在想减少下一个查询的执行时间。我已经做了很多研究，但没有发现任何可以帮助我的东西。该查询大约需要六个小时才能完成执行。我遇到的一个主要问题是我无法使用索引，是的，这很重要。

我的想法是，由于我不是SQL专家，所以也许我没有使用最佳实践来实现此查询所需的结果。

我正在处理大量的联接，聚合，临时表等。也许，由于我的经验不足，有些解决方法是我不知道的。因此，也许您可以帮助我。

SELECT  
    ROW_NUMBER() over (ORDER BY C.CourseKey) AS 'RowNumber',
    C.CourseKey,
    COALESCE(DCC.College,C.College) 'College',
    COALESCE(DCC.Department,C.Department) 'Department',
    COALESCE(DCC.CourseNumber,C.CourseNumber) 'CourseNumber',
    COALESCE(DCC.[Subject],C.[Subject]) 'Subject',
    C.Description + ' ('+C.BatchUID+')' as 'CourseSimple',
    COALESCE(DCC.[Description],C.[Description]) as 'Section',
    F.AcademicYear,
    F.Description as 'Term',
    --E.Description as 'Instructor',
    B.Description as 'Item',
    B.CourseItemGroup,
    G.FullDate,
    C.StartDate,
    DU.UserKey,
    SUM(A.CourseItemMinutes) AS 'Minutes',
    SUM(A.CourseItemAccesses) As 'Items'
Into #CourseDesign
FROM Final.FactCourseItemActivity A
INNER JOIN Final.DimCourseItemType B on A.CourseItemTypeKey = B.CourseItemTypeKey
INNER JOIN Final.DimCourse C on A.CourseKey = C.CourseKey
INNER JOIN Final.DimUser DU on A.UserKey = DU.UserKey
INNER JOIN Final.FactStudentCourseSummary FSCS on FSCS.UserSourceKey = DU.SourceKey
                                                    And FSCS.CourseKey = A.CourseKey
                                                    And A.TermKey = FSCS.TermKey
INNER JOIN CustomFinal.DimCourseCustom DCC on FSCS.CourseCustomKey = DCC.CourseCustomKey
INNER JOIN Final.DimTerm F on A.TermKey = F.TermKey
INNER JOIN Final.DimDate G on A.DateKey = G.DateKey
WHERE A.CourseItemMinutes > 0
GROUP BY 
    C.CourseKey,
    COALESCE(DCC.College,C.College),
    COALESCE(DCC.Department,C.Department),
    COALESCE(DCC.CourseNumber,C.CourseNumber),
    COALESCE(DCC.[Subject],C.[Subject]),
    C.Description + ' ('+C.BatchUID+')',
    COALESCE(DCC.[Description],C.[Description]),
    F.AcademicYear,
    F.Description,
    --E.Description,
    B.Description,
    B.CourseItemGroup,
    G.FullDate,
    C.StartDate,
    DU.UserKey


Select 
       A.RowNumber,
       A.Coursekey,
       A.College,
       A.Department,
       A.CourseNumber,
       A.[Subject],
       A.CourseSimple,
       A.Section,
       A.AcademicYear,
       A.Term,
       A.Item,
       A.CourseItemGroup,
       A.FullDate,
       H.WeekLevel,
       SUM(A.[Minutes]) 'Minutes',
       COUNT(Distinct A.UserKey) 'Students',
       SUM(A.Items) 'Items'
Into #FinalTable
From #CourseDesign A
     INNER JOIN Final.DimDayOfTerm H on 
                case 
                    when A.FullDate is null then -2
                    when DATEDIFF(dd,A.StartDate,A.FullDate)+1 < 0 then -1
                    else DATEDIFF(dd,A.StartDate,A.FullDate)
                end = H.DayOfTermKey
Group by 
         A.RowNumber,
         A.Coursekey,
         A.College,
         A.Department,
         A.CourseNumber,
         A.[Subject],
         A.CourseSimple,
         A.Section,
         A.AcademicYear,
         A.Term,
         A.Item,
         A.CourseItemGroup,
         A.FullDate,
         H.WeekLevel


Select A.RowNumber,
       A.Coursekey,
       A.College,
       A.Department,
       A.CourseNumber,
       A.[Subject],
       A.CourseSimple,
       A.Section,
       A.AcademicYear,
       A.Term,
       A.Item,
       A.CourseItemGroup,
       A.FullDate,
       A.WeekLevel,
       STUFF((SELECT ', ' + DU2.Description
       FROM #FinalTable AS A2
               LEFT OUTER JOIN CustomFinal.ReportingInstructors RI2
                        on A2.CourseKey = RI2.CourseKey
               LEFT OUTER JOIN Final.DimUser DU2
                        on RI2.UserKey = DU2.UserKey
               WHERE ((A.RowNumber IS NULL AND A2.RowNumber IS NULL) OR A.RowNumber = A2.RowNumber)
       FOR XML PATH('')), 1, 2, '') AS Instructor,
       A.Minutes,
       A.Students,
       A.Items
From #FinalTable A
LEFT OUTER JOIN CustomFinal.ReportingInstructors RI on A.CourseKey = RI.CourseKey
LEFT OUTER JOIN Final.DimUser DU on RI.UserKey = DU.UserKey

Group by 
         A.RowNumber,
         A.Coursekey,
         A.College,
         A.Department,
         A.CourseNumber,
         A.[Subject],
         A.CourseSimple,
         A.Section,
         A.AcademicYear,
         A.Term,
         A.Item,
         A.CourseItemGroup,
         A.FullDate,
         A.WeekLevel,
         A.Minutes,
         A.Students,
         A.Items

Answer 1

最近，我不得不将大量数据从一个数据库传输到另一个数据库。在将数据插入到目标中时，我不得不想出一种不会削弱我的源SQL Server的方法。

这就是我要做的。如果您正在做类似的事情，也许这也会对您有帮助。

insert_more_rows:

    INSERT INTO MyDestination (
        cols ...
    )
    SELECT TOP 1000
        cols ...
    FROM MySource
    WHERE
        NOT EXISTS ( condition to exclude existing data )...

IF ( ( some condition to determine there are more rows ) > 0 )
    GOTO insert_more_rows;

这对我来说效果很好，并大大减少了所涉及的时间。

SQL查询，需要几个小时才能完成执行

1 个答案: