在光标中选择查询花费太长时间

Question

我设计了一个游标来针对 6500 名检查员运行一些统计信息，但花费的时间太长。游标中还有许多其他选择查询，但它们运行正常，但以下选择运行非常缓慢。没有光标选择查询运行得很好。

要求：

访问已上传文件的每个检查员的访问次数（1 次或 2 次或 13 次）

表格：

• Inspectors: InspectorID
• InspectionScope: ScopeID, InspectorID (FK)
• Visits: VisitID, VisitDate ScopeID (FK)
• VisitsDoc: DocID, DocType, VisitID (FK)

光标代码：

DECLARE 
        @curInspID int, 
        @DateFrom date, @DateTo date;

SELECT @DateTo = CAST(GETDATE() AS DATE)
       ,@DateFrom = CAST(GETDATE() - 90 AS DATE)


DECLARE  
        @InspectorID int,
        @TotalVisits int;


DECLARE @Report TABLE (
        InspectorID int,
        TotalVisits int)


DECLARE curList CURSOR FOR
    SELECT InspectorID FROM Inspectors ;        


OPEN curList
FETCH NEXT FROM curList INTO @curInspID;

WHILE @@FETCH_STATUS = 0
BEGIN

SELECT 
    @curInspID = s.InspectorID    
    ,@TotalVisits = COUNT(distinct v.visitID)
from Visits v 
inner join InspectionScope s on s.ScopeID = v.ScopeID 
inner join VisitDocs vd on vd.VisitID = v.VisitID 
where s.InspectorID = @curInspID and vd.DocType IN (1,2,13) 
and v.VisitDate BETWEEN @DateFrom and @DateTo
group by s.InspectorID 


INSERT INTO @Report VALUES(@curInspID,@TotalVisits);

FETCH NEXT FROM curList INTO @curInspID;
END

CLOSE curList
DEALLOCATE curList

SELECT * FROM @Report

以下查询在同一光标内运行正常

    ,@TotalVisitsWithReportScore = (select COUNT(v.visitid) from visits v
                        inner join InspectionScope s on s.ScopeID = v.ScopeID 
                        where v.ReportStandard not in (0,9) and v.VisitType = 1
                            and v.VisitDate BETWEEN @DateFrom and @DateTo
                            and s.InspectorID = @curInspID 
                            )

    ,@TotalVisitsWith_ReportScore_RejectionFeedBack = (select COUNT(v.visitid) from visits v
                        inner join InspectionScope s on s.ScopeID = v.ScopeID 
                        where v.ReportStandard not in (0,9) and v.VisitType = 1
                            and v.DiscrepancyType IN (2,5,6,7,8)
                            and v.VisitDate BETWEEN @DateFrom and @DateTo
                            and s.InspectorID = @curInspID 
                    )

Answer 1

这里不需要光标——您可以使用INSERT INTO 和SELECT，加入Inspector 表。

INSERT INTO @Report 
SELECT 
    s.InspectorID    
    , COUNT(distinct v.visitID)
from Visits v 
    inner join InspectionScope s on s.ScopeID = v.ScopeID 
    inner join VisitDocs vd on vd.VisitID = v.VisitID 
    inner join Inspector i on s.InspectorID = i.InspectorId 
where vd.DocType IN (1,2,13) 
and v.VisitDate BETWEEN @DateFrom and @DateTo
group by s.InspectorID 

---

请注意，如果 Inspector 表中存在其他表中不存在的结果，则您可能需要将 OUTER JOIN 与表一起使用。取决于您的数据和期望的结果。

Answer 2

加快光标速度的最佳方法是.... 摆脱它！

在这里，您绝对不需要光标 - 一个简单的 SELECT 就可以了 - 而且应该明显更快！

DECLARE @Report TABLE (InspectorID int, TotalVisits int)

DECLARE curList CURSOR FOR
    SELECT InspectorID FROM Inspectors ;        


OPEN curList
FETCH NEXT FROM curList INTO @curInspID;

WHILE @@FETCH_STATUS = 0
BEGIN

INSERT INTO @Report (InspectorID, TotalVisits)
   SELECT 
      i.InspectorID,
      COUNT(v.visitID)
   FROM 
      dbo.Inspectors i
   INNER JOIN
      dbo.InspectionScope s ON s.InspectorId = i.InspectorId
   INNER JOIN
      dbo.Visits v ON s.ScopeID = v.ScopeID 
   INNER JOIN
      dbo.VisitDocs vd ON vd.VisitID = v.VisitID 
   WHERE 
      vd.DocType IN (1, 2, 13) 
      AND v.VisitDate BETWEEN @DateFrom AND @DateTo
   GROUP BY
      s.InspectorID 

SELECT * FROM @Report

Answer 3

不再推荐使用光标。最好将数据插入临时表并为其添加主键。

因此，在您的循环中，您将有一个 while 循环，该循环使用临时表中您的 Id 上的 WHERE 子句循环遍历您的表。

这要快得多。