sql - 查询调整 SQL Server 2008

Question

我有一个 View 名称“vw_AllJobsWithRecruiter”。

ALTER VIEW dbo.vw_AllJobsWithRecruiter
AS
SELECT TOP(SELECT COUNT(iJobID_PK) FROM dbo.tbUS_Jobs)
         iJobId_PK AS JobId,
         dbo.ufn_JobStatus(iJobId_PK) AS JobStatus,
         dbo.ufn_RecruiterCompanyName(iJobId_PK) AS CompanyName,
         sOther AS OtherCompanyName
FROM dbo.tbUS_Jobs
WHERE bDraft = 0
ORDER BY dtPostedDate DESC

此 View 仅包含 3278 行。

如果我执行以下查询:

SELECT * FROM vw_AllJobsWithRecruiter
WHERE  OtherCompanyName LIKE '%Microsoft INC%'

执行时间不到一秒。

现在我的问题是:

如果我使用下面的查询:

SELECT * FROM vw_AllJobsWithRecruiter
WHERE CompanyName LIKE '%Microsoft INC%' 
      OR OtherCompanyName LIKE '%Microsoft INC%'

执行需要 30 秒，前端会抛出超时错误。函数在这里:

CREATE Function [dbo].[ufn_RecruiterCompanyName] (@JobId bigint)      
RETURNS nvarchar(200)      
AS      
BEGIN      
 DECLARE @ResultVar nvarchar(200)     
 DECLARE @RecruiterId bigint     

 select @RecruiterId = iRecruiterId_FK from dbo.tbUS_Jobs     with (Nolock)   
 where iJobId_PK = @JobId;      

 Select @ResultVar = sCompanyName from dbo.tbUS_RecruiterCompanyInfo     with (Nolock)   
 where iRecruiterId_FK = dbo.ufn_GetParentRecruiterID(@RecruiterId)      

 return isnull(@ResultVar,'')      

END 

其他功能

CREATE Function [dbo].[ufn_GetParentRecruiterID](@RecruiterId bigint)  
returns bigint  
as  
begin   
declare @ParentRecruiterId bigint  

SELECT @ParentRecruiterId = iParentId FROM dbo.tbUS_Recruiter with (Nolock)   
WHERE iRecruiterId_PK = @RecruiterId  

IF(@ParentRecruiterId = 0)  
 SET @ParentRecruiterId = @RecruiterId  

RETURN @ParentRecruiterId  
end 

我的问题是

1. Why it is taking so much time to execute?
2. How can I reduce the execution time?

非常感谢您的关注。

Answer 1

第一个查询只为返回的行调用 dbo.ufn_RecruiterCompanyName()，它过滤存储的值。对于第二个查询，SQL Server 需要为所有行调用 ufn。根据功能的不同，这可能会导致延迟。

在查询分析器中检查这个，并尽量避免第二个查询 ^^

查看自定义函数后，我建议使用连接表重写该 View 。在此类函数中进行查找时，SQL Server 会为它接触或传递的每一行调用它们。使用 LEFT JOIN 允许服务器更快地使用索引和键，并且应该在不到一秒的时间内交付数据。

如果没有所有自定义函数和所有表的定义，我无法为您提供新 View 的示例，但它看起来应该有点像这样:

SELECT
    jobs.Jobid,
    jobstatus.Jobstatus,
    recruiter.Company
FROM jobs
LEFT JOIN jobstatus ON jobs.Jobid = jobstatus.Jobid
LEFT JOIN recruiter ON jobs.Recruiterid = recruiter.Recruiterid