优化复杂的SQL查询

Question

我正在使用Azure SQL Server数据库。 我已经编写了一个sql查询来生成reprot。 这里是：

;WITH cte AS
(
  SELECT ProjectID, CreatedDateUTC, ProductID, LicenseID, BackgroundID from Project p 
  WHERE  CAST(p.CreatedDateUTC AS DATE) >= @StartDate and CAST(p.CreatedDateUTC AS DATE) <= @EndDate 
  and IsBackgroundUsed = 1
  and s7ImageGenerated = 1  and p.SiteCode in ('b2c' )
)
SELECT ProjectID , CreatedDateUTC,
(SELECT BackgroundName from Background b WHERE b.BackgroundID = cte.BackgroundID) AS BackgroundName,
(SELECT Name FROM Product pr WHERE pr.ProductID = cte.ProductID) AS ProductName,
Case WHEN LicenseID is null THEN 'Standard' ELSE (SELECT LicenseName from License l WHERE l.LicenseID = cte.LicenseID) END AS CLA,
(SELECT PurchaseFG from Product_background pb WHERE pb.BackgroundID = cte.BackgroundID and pb.ProductId = cte.productID) AS PurchaseFG,
(SELECT FGcode from Product pr WHERE pr.ProductID = cte.ProductID) AS ProductFGCode,
--(Select dbo.[getProjectFGCodeByBackground](cte.ProductID, cte.BackgroundID)) AS FGCode,
'' AS ERPOrderNumber,
0 AS DesignQuanity
from cte
WHERE (SELECT count(*) from Approval.OrderDetail od WHERE od.ProjectID = cte.ProjectID) = 0

有什么方法可以优化此查询。 超时问题来了。 我已经在存储过程中编写了此查询，并使用linq实体框架调用了该存储过程。

之前我曾使用过join，但它的速度较慢，因此尝试使用子查询。 工作超过一年，现在不工作。

Answer 1

这肯定会提高性能，尤其是在表Approval.OrderDetail大的情况下：

...WHERE not exists
(SELECT 1 from Approval.OrderDetail od WHERE od.ProjectID = cte.ProjectID)

Answer 2

为每个单个字段编写子选择是一种检索数据的糟糕方法，因为您最终可能会遇到很多循环联接，这些联接在大型数据集上的性能很差。

您可以使用原始的JOIN方法，但是您需要确保在连接列上具有适当的索引。

您还可以用LEFT JOIN和IS NULL组合替换WHERE子句

LEFT JOIN Approval.OrderDetail od
ON od.ProjectID = p.ProjectID
...
AND od.ProjectID IS NULL;

或NOT EXISTS （尽管对于主查询返回的每一行更可能必须扫描更大范围的行）。

WHERE NOT EXISTS 
(SELECT 1 FROM Approval.OrderDetail od WHERE od.ProjectID = cte.ProjectID)

无论哪种情况，请确保对Project表进行适当的索引(IsBackgroundUsed, s7ImageGenerated, SiteCode, CreatedDate)并确保对所有联接进行适当的索引。

我还要问您是否真的需要将CreatedDateUTC字段转换为DATE类型？

可能的简化可能是：

SELECT
    p.ProjectID,
    p.CreatedDateUTC,
    b.BackgroundName,
    pr.Name,
    IIF(p.LicenseID IS NULL, 'Standard', l.LicenseName) AS CLA,
    pb.PurchaseFG,
    pr.FGCode AS ProductFGCode,
    '' AS ERPOrderNumber,
    0 AS DesignQuantity
FROM Project p
LEFT JOIN Approval.OrderDetail od
ON od.ProjectID = p.ProjectID
LEFT JOIN Background b
ON b.BackgroundID = p.BackgroundID
LEFT JOIN Product pr 
ON pr.ProductID = p.ProductID
LEFT JOIN License l
ON l.LicenseID = p.LicenseID
LEFT JOIN Product_Background pb
ON pb.BackgroundID = p.BackgroundID
AND pb.ProductID = p.ProductID
WHERE p.CreatedDateUTC >= @StartDate AND p.CreatedDateUTC <= @EndDate
  AND p.IsBackgroundUsed = 1
  AND p.s7ImageGenerated = 1 
  AND p.SiteCode = 'b2c'
  AND od.ProjectID IS NULL;

Answer 3

WHERE  CAST(p.CreatedDateUTC AS DATE) >= @StartDate and CAST(p.CreatedDateUTC AS DATE) <= @EndDate 

进行此SARGAble，在CreatedDateUTC上创建非聚集索引

假设这是参数，

 declare @StartDate datetime='2018-02-01'
 declare @EndDate datetime='2018-02-28'

然后，

set @EndDate=dateadd(second,-1,dateadd(day,1,@EndDate))

现在您可以放心使用了，

WHERE  p.CreatedDateUTC  >= @StartDate and p.CreatedDateUTC  <= @EndDate 

我认为@Mark Sinkinson查询将比子查询好用（我将尝试一次NOT EXISTS子句）

尽可能使用INNER JOIN。 希望您正在使用存储过程并调用SP。

在所有联接列上创建索引。

由于您的子查询在没有TOP 1的情况下可以正常输出，因此看来所有表与Project都具有一对一的关系。

CREATE NONCLUSTERED INDEX IX_Project ON project (
    CreatedDateUTC
    ,IsBackgroundUsed
    ,s7ImageGenerated
    ,SiteCode
    ) include (ProductID,LicenseID,BackgroundID);

希望projectID已经是聚簇索引。

Answer 4

可能不会更快，但对我来说更容易阅读。

您应该可以调整@StartDate和@EndDate，而不必强制转换为最新日期。

有一个关于所有联接和条件的索引。

如果这些是FK，则您应该能够（并且应该）使用内部联接。

SELECT P.ProjectID , P.CreatedDateUTC,
       b.BackgroundName,
       pr.Name AS ProductName, 
       isnull(l.LicenseName, 'Standard') as CLA,
       pb.PurchaseFG,
       pr.FGcode AS ProductFGCode,
       '' AS ERPOrderNumber,
       0  AS DesignQuanity
 from Project p 
 left join Background b 
   on b.BackgroundID  = p.BackgroundID 
 left join Product pr
   on pr.ProductID    = p.ProductID 
 left join License l 
   on l.LicenseID     = p.LicenseID 
 left join Product_background pb 
   on pb.BackgroundID = p.BackgroundID 
  and pb.ProductId    = p.productID
 left join Product pr 
   on pr.ProductID    = p.ProductID
WHERE CAST(p.CreatedDateUTC AS DATE) >= @StartDate 
  and CAST(p.CreatedDateUTC AS DATE) <= @EndDate 
  and p.IsBackgroundUsed = 1
  and p.s7ImageGenerated = 1  
  and p.SiteCode = 'b2c'
  and not exists (SELECT 1 
                  from Approval.OrderDetail od 
                  WHERE od.ProjectID = p.ProjectID)