Sql 我的查询需要很长时间才能执行

您可以使用联接而不是相关子查询重写查询：

SELECT DISTINCT servRole,
                (SELECT PositionLongtext
                 FROM   tblPositionMaster tpm
                 WHERE  tsc.servRole = tpm.tblID)         AS ServPositionID,
                (SELECT EmployeeName
                 FROM   tblEmployeeList te
                 WHERE  tsc.ECNoServ = te.ECNo
                        AND te.PeriodName = @PeriodName)  AS SERVName,
                (SELECT ECNo
                 FROM   tblEmployeeList tl
                 WHERE  tsc.ECNoServ = tl.ECNo
                        AND tl.PeriodName = @PeriodName)  AS ECNoServ,
                CustRole,
                (SELECT PositionLongtext
                 FROM   tblPositionMaster tpm
                 WHERE  tsc.CustRole = tpm.tblID)         AS CustPositionID,
                (SELECT EmployeeName
                 FROM   tblEmployeeList tm
                 WHERE  tsc.ECNOCust = tm.ECNo
                        AND tm.PeriodName = @PeriodName)  AS CUSTName,
                (SELECT ECNo
                 FROM   tblEmployeeList tel
                 WHERE  tsc.ECNOCust = tel.ECNo
                        AND tel.PeriodName = @PeriodName) AS ECNOCust,
                (SELECT DirectoryName
                 FROM   tblAttributeDirectory td
                 WHERE  td.DirectoryID = tsc.DirectoryID) AS DirectoryName,
                (SELECT DirectoryID
                 FROM   tblAttributeDirectory td
                 WHERE  td.DirectoryID = tsc.DirectoryID) AS DirectoryID,
                FinalscoreEmp,
                Flag
FROM   tblServToCustMapping tsc
WHERE  tsc.PeriodName = @PeriodName
ORDER  BY ECNoServ 

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我看不到任何问题，你可以把这个查询重写得更简单。这里没有任何不精确的东西。但我会创建它。我不擅长sql。@SudhirYadav-你应该阅读这篇文章阅读基本sql教程，查找内部联接章节。它给出错误，“无法绑定多部分标识符t1.ECNo”。@SudhirYadav-很抱歉，它是tl而不是t1。我更新了我的答案，请尝试我的eidt。

SELECT DISTINCT 
  servRole,
  tpm.PositionLongtext AS ServPositionID,
  te.EmployeeName AS SERVName, 
  tl. ECNo AS ECNoServ,
  CustRole,
  tpm.PositionLongtext AS CustPositionID,
  tm.EmployeeName AS CUSTName,
  tel.ECNo AS ECNOCust,
  td2.DirectoryName AS DirectoryName,
  td2.DirectoryID AS DirectoryID,
  FinalscoreEmp,
  Flag
FROM   tblServToCustMapping      tsc
INNER JOIN tblPositionMaster     tpm ON tsc.servRole   = tpm.tblID
INNER JOIN tblEmployeeList       te  ON tsc.ECNoServ   = te.ECNo
INNER JOIN tblEmployeeList       tl  ON tsc.ECNoServ   = tl.ECNo
INNER JOIN tblPositionMaster     tpm ON tsc.CustRole   = tpm.tblID
INNER JOIN tblEmployeeList       tm  ON tsc.ECNOCust   = tm.ECNo
INNER JOIN tblEmployeeList       tel ON tsc.ECNOCust   = tel.ECNo
INNER JOIN tblAttributeDirectory td1 ON td.DirectoryID = tsc.DirectoryID
INNER JOIN tblAttributeDirectory td2 ON td.DirectoryID = tsc.DirectoryID
WHERE tsc.PeriodName = @PeriodName
  AND te.PeriodName  = @PeriodName
  AND tl.PeriodName  = @PeriodName
  AND tel.PeriodName = @PeriodName
  AND tm.PeriodName  = @PeriodName
ORDER  BY ECNoServ;