在光标中选择查询需要太长时间

Question

我设计了一个游标来针对6500个检查器运行一些统计数据，但它耗时太长。游标中还有许多其他选择查询，但它们运行正常，但以下选择运行速度非常慢。没有光标选择查询运行完美。

要求：

• Inspectors: InspectorID
• InspectionScope: ScopeID, InspectorID (FK)
：

对于其中的访问已上传文档（1或2或13），每个检查员

表访问次数

• 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 

以下查询运行相同的光标

,@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

无需在这里光标里面好 - 你可以使用INSERT INTO与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，你可能需要，如果有结果，在该表中没有其他表中存在使用OUTER JOIN与Inspector表。取决于你的数据和期望的结果。

Answer 2

加速游标的最佳方式是...... 摆脱它！

在这里，你肯定不需要光标 - 一个简单的SELECT会做 - 而且应该大幅更快！

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

不推荐使用游标。将数据插入临时表并向其中添加主键会更好。

所以在你的循环中，你将有一个while循环，在你的表中用你的Id中的WHERE子句遍历你的表。

这要快得多。