執行SQL請求花費很多時間

我有一個SQL查詢需要15秒，有時需要1分鐘。請告訴我，我可以做我的查詢更輕。執行SQL請求花費很多時間

SELECT TOP 100 
u.firstName, 
u.id as userID, 
ueh.targetID, 
ueh.opened, 
ueh.emailID, 
u.phone, 
u.gender 
FROM dbo.Students u 
INNER JOIN dbo.tblEmailHistory ueh 
ON ueh.studentID = u.ID 
WHERE (CONVERT(date,DATEADD(day,6,ueh.sDate))=CONVERT(date,getdate())) 
AND IsNull(u.firstName, '') != '' 
AND IsNull(u.email, '')  != '' 
AND IsNull(u.phone, '')  != '' 
AND ueh.status = 'sent' 
AND ueh.reject_reason = 'null' 
AND ueh.targetID = 28 
AND ueh.opened = 0 
AND u.deleted = 0 
AND NOT EXISTS (SELECT ush.smsSendFullDate, ush.studentID FROM dbo.UsersSmsHistory ush WHERE u.id = ush.studentID AND DATEDIFF(DAY,ush.smsSendFullDate,GETDATE()) = 0)

來源

2017-06-25 Edward Gizbreht

您是否已檢查執行計劃？ –

這是您的查詢大大簡化：

SELECT TOP 100 u.firstName, u.id as userID, 
     ueh.targetID, ueh.opened, ueh.emailID, 
     u.phone, u.gender 
FROM dbo.Students u INNER JOIN 
    dbo.tblEmailHistory ueh 
    ON ueh.studentID = u.ID 
WHERE ueh.sDate >= cast(getdate() + 6 as date) AND 
     ueh.sDate < csat(getdate() + 7 as date) AND 
     u.firstName <> '' AND 
     u.email <> '' AND 
     u.phone <> '' AND 
     ueh.status = 'sent' AND 
     ueh.reject_reason = 'null' AND -- sure you mean a string here? 
     ueh.targetID = 28 AND 
     ueh.opened = 0 AND 
     u.deleted = 0 AND 
     NOT EXISTS (SELECT ush.smsSendFullDate, ush.studentID 
        FROM dbo.UsersSmsHistory ush 
        WHERE u.id = ush.studentID AND 
         convert(date, ush.smsSendFullDate) = convert(date, GETDATE()) 
       );

注：比較來NULL從不幾乎所有的比較真實，所以ISNULL()/COALESCE()是不必要的。

然後開始添加索引。我建議：

tblEmailHistory(targetid, status, opened, deleted, rejectreason, sdate)
UsersSmsHistory(studentID, smsSendFullDate)

我猜大多數學生有姓名和電話號碼，所以對這些列的索引將不會幫助。

來源

2017-06-25 13:03:44

沒有幫助，謝謝 –

@EdwardGizbreht。。。你添加了索引嗎？ –

它工作！謝謝！ –

您的查詢看起來沒問題，沒有多餘的零件。花費大量時間的原因是因爲您要連接三次表格，並且可能會有很多數據。因此，除了改善您的查詢外，還可以嘗試通過在dbo.tblEmailHistory.studentID,dbo.Students.ID等列上添加index來提高表的性能。

來源

2017-06-25 13:03:44

執行SQL請求花費很多時間

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