改进此SQL查询以获得更好的性能

Question

DBA不喜欢我使用带有子查询的case语句。 我还有其他方法可以提高性能吗？ 此更新语句是存储过程的一部分。

    UPDATE dbo.CMN_PersonsFerpa 
    SET 
        IsWorkEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Work'  THEN @IsFERPA ELSE IsWorkEmailFerpa END,
        IsPersonalEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Personal'  THEN @IsFERPA ELSE IsPersonalEmailFerpa END,
        IsParentEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Parent'  THEN @IsFERPA ELSE IsParentEmailFerpa END,
        IsTempEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Temporary'  THEN @IsFERPA ELSE IsTempEmailFerpa END,
        IsFAFSAEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'FAFSA'  THEN @IsFERPA ELSE IsFAFSAEmailFerpa END,
        IsCSSProfEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'CSS Profile'  THEN @IsFERPA ELSE IsCSSProfEmailFerpa END,
        IsCommenceEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Commencement'  THEN @IsFERPA ELSE IsCommenceEmailFerpa END,
        IsAcctHoldEmailFerpa = (CASE WHEN (SELECT EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID) =  'Account Holder'  THEN @IsFERPA ELSE IsAcctHoldEmailFerpa END
    Where CMN_PersonsFerpa.cmn_personsID = (select cmn_personsID from CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID)

经过几个建议，这就是我的意思。 这可以接受吗？ 或者，还有更好的方法？：

    SELECT @DBType = EmailType, @cmn_personsID = CMN_PersonsID FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID

    UPDATE dbo.CMN_PersonsFerpa 
    SET 
        IsWorkEmailFerpa = CASE WHEN @DBType =  'Work'  THEN @IsFERPA END,
        IsPersonalEmailFerpa = CASE WHEN @DBType =  'Personal'  THEN @IsFERPA END,
        IsParentEmailFerpa = CASE WHEN @DBType = 'Parent'  THEN @IsFERPA END,
        IsTempEmailFerpa = CASE WHEN @DBType =  'Temporary'  THEN @IsFERPA END,
        IsFAFSAEmailFerpa = CASE WHEN @DBType =  'FAFSA'  THEN @IsFERPA END,
        IsCSSProfEmailFerpa = CASE WHEN @DBType =  'CSS Profile'  THEN @IsFERPA END,
        IsCommenceEmailFerpa = CASE WHEN @DBType =  'Commencement'  THEN @IsFERPA END,
        IsAcctHoldEmailFerpa = CASE WHEN @DBType =  'Account Holder'  THEN @IsFERPA END,
        LastChangeBy = @UserGUID,
        LastChangeDateTime = GETDATE()
            Where CMN_PersonsFerpa.cmn_personsID = @CMN_PersonsID

Answer 1

目标是消除子查询。 您可以通过在更新前建立一个临时表或使用适当的链接来做到这一点。 在不知道您的数据模式的情况下，很难帮助您设计一些东西，但是这里有一个镜头：

update p set 
    IsWorkEmailFerpa = case when e.EmailType = 'Work' then @IsFERPA else IsWorkEmailFerpa end,
    IsPersonalEmailFerpa = case when e.EmailType = 'Personal' then @IsFERPA else IsPersonalEmailFerpa end,
    IsParentEmailFerpa = case when e.EmailType = 'Parent' then @IsFERPA else IsParentEmailFerpa end,
    IsTempEmailFerpa = case when e.EmailType = 'Temporary' then @IsFERPA else IsTempEmailFerpa end,
    ...
    IsAcctHoldEmailFerpa = case when e.EmailType = 'Account Holder' then @IsFERPA else IsAcctHoldEmailFerpa end,
from  dbo.CMN_PersonsFerpa  p
    join dbo.CMN_PersonsEmailLinks e
        on e.cmn_personsID = p.cmn_personsID
where e.CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID

Answer 2

为什么不使用联接？ 相关子查询像游标一样逐行工作，几乎不应该使用。

Answer 3

与其将查询运行8次，不如将其运行到变量中一次并对变量本身执行案例。

看起来像这样：

SELECT @EmailType = EmailType FROM dbo.CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID

UPDATE dbo.CMN_PersonsFerpa 
    SET 
        IsWorkEmailFerpa = (CASE WHEN @EmailType =  'Work'  THEN @IsFERPA ELSE IsWorkEmailFerpa END,
        IsPersonalEmailFerpa = (CASE WHEN @EmailType =  'Personal'  THEN @IsFERPA ELSE IsPersonalEmailFerpa END,
        IsParentEmailFerpa = (CASE WHEN @EmailType =  'Parent'  THEN @IsFERPA ELSE IsParentEmailFerpa END,
        IsTempEmailFerpa = (CASE WHEN @EmailType =  'Temporary'  THEN @IsFERPA ELSE IsTempEmailFerpa END,
        IsFAFSAEmailFerpa = (CASE WHEN @EmailType =  'FAFSA'  THEN @IsFERPA ELSE IsFAFSAEmailFerpa END,
        IsCSSProfEmailFerpa = (CASE WHEN @EmailType =  'CSS Profile'  THEN @IsFERPA ELSE IsCSSProfEmailFerpa END,
        IsCommenceEmailFerpa = (CASE WHEN @EmailType =  'Commencement'  THEN @IsFERPA ELSE IsCommenceEmailFerpa END,
        IsAcctHoldEmailFerpa = (CASE WHEN @EmailType =  'Account Holder'  THEN @IsFERPA ELSE IsAcctHoldEmailFerpa END
    Where CMN_PersonsFerpa.cmn_personsID = (select cmn_personsID from CMN_PersonsEmailLinks WHERE CMN_PersonsEmailLinksID = @CMN_PersonsEmailLinksID)