如何提高在下文提到的SQL查询

Question

文本列的性能有一个SQL工会与工会3所有查询的所有查询。在查询中添加了文本列CAST(c.getQuestionId AS VARCHAR(300))后，查询执行时间发生了显着变化。正在使用的数据库是SQL SERVER 2014.性能调优专家，请帮助。

上有JcccustomersAssessmentProxy创造3项指标。这是一张拥有8000万条记录的表格。显式索引的使用只在第三查询中只提到了 （即（NOLOCK, INDEX=IX_AssessmentProxy_myJcAssessmentContext））

有上myJcAssessmentContext

一个非聚集索引

有上getmycoordtoyplanver一个非聚集索引

有一种getMyEventItem上的非聚簇索引

SELECT  ass.P_KEY 
      ,ass.SS_CODE 
      ,CAST(evp.EVENT_SSID AS VARCHAR(11)) AS EVENT_SSID 
      ,CAST(QUESTIONNUMBER AS VARCHAR(3))        AS EVENT_NO 
      ,CAST(ISNULL(CAST(TEMPLATEVERSION AS VARCHAR), 0) AS INT)  AS TEMPLATEVERSION 
      ,ISNULL(CAST(TEMPLATENAME AS VARCHAR(50)), ' ')     AS TEMPLATENAME 
      ,evp.ASS_DATE 
      ,ISNULL(ANSWERNUMBER, 0)          AS ANSWER_NO 
      ,ass.CASE_SSID 
      ,ass.RE_SSID 
      ,ass.RE_DATE 
      ,ass.EPISODE_SSID 
      ,ass.[SERVICE] 
      ,ass.SERVICE_DESC 
      ,ass.TAM_KEY 
      ,ass.PRv_KEY 
      ,CAST(QUESTIONNUMBER AS VARCHAR(3))     AS QUESTION_NO 
      ,ISNULL(CONVERT(VARCHAR(100), REPLACE(REPLACE(CAST(QUESTIONTEXT AS VARCHAR(650)), char(10), ''), char(13), ' ')), ' ') AS QUESTION_TEXT 
      ,ISNULL(CAST(ANSWER AS VARCHAR(125)), ' ')   AS ANSWER_TEXT 
      ,a.MyAssessment          AS ASSESSMENT_SSID 
----------------------------------------------------------------------------------------- 

      ,CAST(RIGHT(a.getMyCoordtoyPlanVer, 10) AS INT)  AS toy_PLAN_VERSION_SSID  
      ,CAST(RIGHT(a.myJcAssessmentContext, 10) AS INT)  AS CONTEXT_FORM_SSID 
-----------------------------------------------------------------------------------------   
      ,ass.RECORD_DATE 
           **,CAST(a.getQuestionId AS VARCHAR(300))     AS QUESTION_ID /*NEW Text Column ,this remove the parallelism*/** 
FROM  SourceFeed.dbo.JcccustomersAssessmentProxy AS a WITH(NOLOCK) 
      INNER JOIN 
      TEMP_DATABASE.dbo.jsystemReport_AllEventItems_AllPersons evp WITH(NOLOCK) 
      ON a.getMyEventItem = evp.oid 


      INNER JOIN 
      TEMP_DATABASE.dbo.jsystemAssessment      ass WITH(NOLOCK) 
      ON evp.getcustomersId = ass.customersID 
      AND evp.EVENT_SSID = ass.EVENTID 


UNION ALL 

SELECT  ass.P_KEY 
      ,ass.SS_CODE 
      ,CAST(csp.ENT_SSID AS VARCHAR(11)) AS EVENT_SSID 
      ,CAST(jcc.QUESTIONNUMBER AS VARCHAR(3)) AS EVENT_NO 
      ,CAST(ISNULL(CAST(CAST(jcc.TEMPLATEVERSION AS VARCHAR) AS VARCHAR), 0) AS INT) AS TEMPLATEVERSION 
      ,ISNULL(CAST(jcc.TEMPLATENAME AS VARCHAR(50)), ' ') AS TEMPLATENAME 
      ,csp.ASSESSMENT_DATE 
      ,ISNULL(jcc.ANSWERNUMBER, 0) AS ANSWER_NO 
      ,ass.CASE_SSID 
      ,ass.REF_SSID 
      ,ass.RE_DATE 
      ,ass.EPISODE_SSID 
      ,ass.[SERVICE] 
      ,ass.SERVICE_DESC 
      ,ass.TEAM_KEY 
      ,ass.PROVIDER_KEY 
      ,CAST(ISNULL(jcc.QUESTIONNUMBER, 0) AS VARCHAR(3)) AS QUESTION_NO 
      ,isnull(CONVERT(VARCHAR(100), replace(replace(CAST(jcc.QUESTIONTEXT AS VARCHAR(650)), char(10), ''), char(13), ' ')), ' ') AS QUESTION_TEXT 
      ,ISNULL(CAST(jcc.ANSWER AS VARCHAR(125)), ' ') AS ANSWER_TEXT 
      ,jcc.MyAssessment AS ASSESSMENT_SSID 
----------------------------------------------------------------------------------------- 

      ,CAST(RIGHT(jcc.getMyCoordtoyPlanVer, 10) AS INT)  AS toy_PLAN_VERSION_SSID  
      ,CAST(RIGHT(jcc.myJcAssessmentContext, 10) AS INT)  AS CONTEXT_FORM_SSID 
-----------------------------------------------------------------------------------------   
      ,ass.RECORD_DATE 
           **,CAST(jcc.getQuestionId AS VARCHAR(300))     AS QUESTION_ID /*NEW Text Column ,this remove the parallelism*/** 
FROM  TEMP_DATABASE.dbo.jsystemReport_toySpell    csp WITH(NOLOCK) 
      INNER JOIN 
      TEMP_DATABASE.dbo.jsystemAssessment      ass WITH(NOLOCK) 
      ON csp.getcustomersId = ass.customersID 
      AND csp.EVENT_SSID = ass.EVENTID 
      LEFT OUTER JOIN 
      SourceFeed.dbo.JcccustomersAssessmentProxy jcc WITH(NOLOCK) 
      ON csp.OID = jcc.getmycoordtoyplanver 

WHERE  NOT EXISTS (SELECT tp1.OID 
         FROM TEMP_DATABASE.dbo.AssessmentTransferPart1 tp1 
         WHERE tp1.OID = jcc.OID) 

UNION ALL 

SELECT  ass.P_KEY 
      ,ass.SS_CODE 
      ,CAST(a.EVENT_SSID AS VARCHAR(11)) AS EVENT_SSID 
      ,CAST(CAST(C.QUESTIONNUMBER AS INT) AS CHAR(3)) AS EVENT_NO 
      ,CAST(ISNULL(CAST(C.TEMPLATEVERSION AS VARCHAR), 0) AS INT) AS TEMPLATEVERSION 
      ,ISNULL(CAST(C.TEMPLATENAME AS VARCHAR(50)), ' ') AS TEMPLATENAME 
      ,a.ASSESSMENT_DATE 
      ,ISNULL(C.ANSWERNUMBER, 0) AS ANSWER_NO 
      ,ass.CASE_SSID 
      ,ass.REL_SSID 
      ,ass.REAL_DATE 
      ,ass.EPISODE_SSID 
      ,ass.[SERVICE] 
      ,ass.SERVICE_DESC 
      ,ass.TEAM_KEY 
      ,ass.PROVIDER_KEY 
      ,CAST(ISNULL(CAST(C.QUESTIONNUMBER AS INT), 0) AS VARCHAR(3)) AS QUESTION_NO 
      ,isnull(CONVERT(VARCHAR(100), CAST(C.QUESTIONTEXT AS VARCHAR(650))), ' ') AS QUESTION_TEXT 
      ,ISNULL(CAST(C.ANSWER AS VARCHAR(125)), ' ') AS ANSWER_TEXT 
      ,a.MyAssessment AS ASSESSMENT_SSID 
----------------------------------------------------------------------------------------- 

      ,CAST(RIGHT(C.getMyCoordtoyPlanVer, 10) AS INT)  AS toy_PLAN_VERSION_SSID  
      ,CAST(RIGHT(C.myJcAssessmentContext, 10) AS INT)  AS CONTEXT_FORM_SSID 
-----------------------------------------------------------------------------------------   
      ,ass.RECORD_DATE 
           **,CAST(c.getQuestionId AS VARCHAR(300))**     AS QUESTION_ID /*NEW Text Column ,this remove the parallelism*/ 
FROM  SourceFeed.dbo.toyClusterReviewAssessment  B WITH(NOLOCK) 
      INNER JOIN 
      SourceFeed.dbo.JcccustomersAssessmentProxy  C WITH(NOLOCK, INDEX=IX_AssessmentProxy_myJcAssessmentContext) 
      ON B.myJCJccUserFormContext = C.myJcAssessmentContext 
      INNER JOIN 
      SourceFeed.dbo.JcccustomersAssessmentScoreProxy D WITH(NOLOCK) 
      ON B.myJCJccUserFormContext = D.myJcAssessmentContext 


      INNER JOIN 
      TEMP_DATABASE.dbo.jsystemReport_toyClusterReviewEvent_AllPersons A WITH(NOLOCK) 
      ON a.myAssessment = B.oid 
      INNER JOIN 
      TEMP_DATABASE.dbo.jsystemAssessment    ass WITH(NOLOCK) 
      ON a.getcustomersId = ass.customersID 
      AND a.EVENT_SSID = ass.EVENTID 
WHERE  NOT EXISTS (SELECT OID 
         FROM (SELECT  tp1.OID 
            FROM TEMP_DATABASE.dbo.AssessmentTransferPart1 tp1 
            UNION ALL 
            SELECT tp2.OID 
            FROM TEMP_DATABASE.dbo.AssessmentTransferPart2 tp2) jcc 
         WHERE jcc.OID = C.OID) 

这是link to the actual execution plan。

---

上JccClientAssessmentProxy jcc添加索引WITH（NOLOCK，INDEX = IX_AssessmentProxy_GETMYCOORDCAREPLANVER）后 这里是the new execution plan。

Answer 1

有问题的部分是：

,CAST(a.getQuestionId AS VARCHAR(300)) AS QUESTION_ID 
    FROM cnlPjccR_Report.dbo.JccClientAssessmentProxy AS a 
     WITH(NOLOCK,INDEX=IX_AssessmentProxy_getMyEventItem) 
    INNER JOIN ... 

和问题重演在你的两个UNION ALL的子查询。

您的执行计划显示价格昂贵Key lookups。

第二种方法是看您可以创建一个“覆盖索引”是 满足整个查询或者至少避免了键查找。一个 “覆盖索引”很简单，就是拥有所有必要要么满足整个查询或在我们的例子中 列的非聚集索引， 消除对键查找操作的需要。一个挑战是要获得 列表，这些列是生成密钥查找的列。您可以通过右击关键 查找运营商做到这一点 在SQL Server Management Studio中（SSMS），然后选择属性。然后在属性窗口中找到输出 列表行，然后单击省略号按钮。 这将打开一个窗口（见下面），其中列出了密钥查找所要查找的所有列 。您可以使用此列表来帮助您确定是否以及如何创建索引以“覆盖”查询或查找关键字 。

在你的情况下列768,16列入创建一个覆盖索引：

[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].answer; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].answerNumber; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].getMyCoordCarePlanVer; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].getQuestionId; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].myAssessment; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].myJcAssessmentContext; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].questionNumber; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].questionText; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].templateName; 
[cnlPjccR_Report].[dbo].[JccClientAssessmentProxy].templateVersion 

可能是你没有索引包括getQuestionId列，这一事实已在你的查询执行计划创建慢Key lookup或RID lookup。

见also here或this answer。