问题
I originally posted the following thread SQL Query - long running / taking up CPU resource
My issue was the SARGABILITY of my query, having addressed that (see the previous thread but in short I was using a lot of ISNULL functions which were bypassing the index scans) I am now having further issues.
My SQL server settings are as below:
cost threshold for parallelism 5
max degree of parallelism 0
My query still takes 2:13 to run and causes CPU / Memory spikes, I have a largely capable server e.g. 64GB RAM so resource is not the issue. See query below:
WITH CTE AS
(
SELECT R.Id AS ResultId,
r.JobId,
r.CandidateId,
R.Email,
CAST(0 AS BIT) AS EmailSent,
NULL AS EmailSentDate,
'PICKUP' AS EmailStatus,
GETDATE() AS CreateDate,
C.Id AS UserId,
C.Email AS UserEmail,
NULL AS Subject
FROM RESULTS R
INNER JOIN JOB J ON R.JobId = J.Id
INNER JOIN Consultant C ON J.UserId = C.Id
WHERE
J.DCApproved = 1
AND (J.Closed = 0 OR J.Closed IS NULL)
AND (R.Email <> '' OR R.Email IS NOT NULL)
AND (R.EmailSent = 0 OR R.EmailSent IS NULL)
AND R.EmailSentDate IS NULL -- email has not been sent
AND (R.EmailStatus = '' OR R.EmailStatus IS NULL)
AND (R.IsEmailSubscribe = 'True' OR R.IsEmailSubscribe IS NULL)
-- not already been emailed for this job
AND NOT EXISTS (
SELECT SMTP.Email
FROM SMTP_Production SMTP
WHERE SMTP.JobId = R.JobId AND SMTP.CandidateId = R.CandidateId
)
-- not unsubscribed
AND NOT EXISTS (
SELECT u.Id FROM Unsubscribe u
WHERE (u.EmailAddress = R.Email OR (u.EmailAddress IS NULL AND R.Email IS NULL))
)
AND NOT EXISTS (
SELECT SMTP.Id FROM SMTP_Production SMTP
WHERE SMTP.EmailStatus = 'PICKUP' AND SMTP.CandidateId = R.CandidateId
)
AND C.Id NOT IN (
-- LIST OF IDS
)
AND J.Id NOT IN (
-- LIST OF IDS
)
AND J.ClientId NOT IN
(
-- LIST OF IDS
)
)
SELECT
CTE.ResultId,
CTE.JobId,
CTE.CandidateId,
CTE.Email,
CTE.EmailSent,
CTE.EmailSentDate,
CTE.EmailStatus,
CTE.CreateDate,
CTE.UserId,
CTE.UserEmail,
NULL
FROM CTE
INNER JOIN
(
SELECT *, row_number() over(partition by CTE.Email, CTE.CandidateId order by CTE.EmailSentDate desc) as rn
FROM CTE
) DCTE ON CTE.ResultId = DCTE.ResultId AND DCTE.rn = 1
See Indexes for the Results table below, something does not seem right on the below:
/****** Object: Index [_dta_index_Results_7_2107154552__K35_K2_K3_K34_K36_K8_K33_K1] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [_dta_index_Results_7_2107154552__K35_K2_K3_K34_K36_K8_K33_K1] ON [dbo].[Results]
(
[EmailSentDate] ASC,
[JobId] ASC,
[AryaCandidateId] ASC,
[EmailSent] ASC,
[EmailStatus] ASC,
[Email] ASC,
[IsEmailSubscribe] ASC,
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [ACI_CMT_APPLICANTS] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [ACI_CMT_APPLICANTS] ON [dbo].[Results]
(
[Email] ASC
)
INCLUDE ( [Id],
[AryaCandidateId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [ACI_Job] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [ACI_Job] ON [dbo].[Results]
(
[AryaCandidateId] ASC,
[JobId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [ACI_Results] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [ACI_Results] ON [dbo].[Results]
(
[AryaCandidateId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [gen_smtp_auto] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [gen_smtp_auto] ON [dbo].[Results]
(
[EmailSentDate] ASC,
[Email] ASC,
[IsEmailSubscribe] ASC,
[EmailSent] ASC,
[EmailStatus] ASC
)
INCLUDE ( [Id],
[JobId],
[AryaCandidateId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Hot] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Hot] ON [dbo].[Results]
(
[JobId] ASC,
[Action] ASC
)
INCLUDE ( [Engaged]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [IX_Results] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [IX_Results] ON [dbo].[Results]
(
[Id] ASC,
[JobId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [IX_Results_1] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [IX_Results_1] ON [dbo].[Results]
(
[Id] ASC,
[JobId] ASC,
[AryaCandidateId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [JobMetrics] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [JobMetrics] ON [dbo].[Results]
(
[JobId] ASC,
[Source] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [KEY_CAMPAIGN] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [KEY_CAMPAIGN] ON [dbo].[Results]
(
[ResumeDownloadedDate] ASC,
[ResumeDownloadStatus] ASC,
[KeywordCampaignId] ASC,
[Source] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [MISSING_CREATEDATE] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [MISSING_CREATEDATE] ON [dbo].[Results]
(
[CreateDate] ASC
)
INCLUDE ( [Id]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [MISSING_MOVERSPROB] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [MISSING_MOVERSPROB] ON [dbo].[Results]
(
[MoversProbability] ASC
)
INCLUDE ( [Id]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [MISSING_SORTORDER] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [MISSING_SORTORDER] ON [dbo].[Results]
(
[SortOrder] ASC
)
INCLUDE ( [Id]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Proto_Resume_Downloa] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Proto_Resume_Downloa] ON [dbo].[Results]
(
[JobId] ASC,
[ResumeDownloadedDate] ASC,
[ResumeDownloadStatus] ASC,
[Location] ASC,
[Source] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Result_Email] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Result_Email] ON [dbo].[Results]
(
[Email] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Result_Email_Send] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Result_Email_Send] ON [dbo].[Results]
(
[EmailSentDate] ASC
)
INCLUDE ( [Id],
[JobId],
[AryaCandidateId],
[Email],
[IsEmailSubscribe],
[EmailSent],
[EmailStatus]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Results_JobId_ACI_Email] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Results_JobId_ACI_Email] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [Id],
[AryaCandidateId],
[Email]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [RESULTS_JOBID_ALL] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [RESULTS_JOBID_ALL] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [Id],
[AryaCandidateId],
[CandidateScore],
[FirstName],
[LastName],
[Telephone],
[Email],
[AddressLine1],
[Location],
[Postcode],
[Resume],
[CurrentJob],
[CurrentCompany],
[Skills],
[Experience],
[Education],
[AryaUpdateDate],
[Industry],
[Source],
[LinkedIn],
[Facebook],
[Twitter],
[MoversLabel],
[MoversProbability],
[SortOrder],
[CreateDate],
[ResumeId],
[IsEmailSubscribe],
[EmailSent],
[EmailSentDate],
[EmailStatus],
[Registered],
[HasVoyagerData],
[Action],
[Engaged],
[FormattedCV],
[CV],
[DerivedSource],
[VoyCode],
[IsEmailEngaged],
[IsSMSEngaged],
[KeywordCampaignId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [ResultsGetResultsbyConsultantId] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [ResultsGetResultsbyConsultantId] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [Id],
[AryaCandidateId],
[CandidateScore],
[FirstName],
[LastName],
[Telephone],
[Email],
[AddressLine1],
[Location],
[Postcode],
[Resume],
[CurrentJob],
[CurrentCompany],
[Skills],
[Experience],
[Education],
[AryaUpdateDate],
[Industry],
[Source],
[LinkedIn],
[Facebook],
[Twitter],
[MoversLabel],
[MoversProbability],
[DOB],
[SortOrder],
[ResumeDownloaded],
[ResumeDownloadedDate],
[ResumeDownloadStatus],
[CreateDate],
[ResumeId],
[IsEmailSubscribe],
[EmailSent],
[EmailSentDate],
[EmailStatus],
[Action],
[Engaged],
[SentToArya],
[IgnoreEmailSent],
[IgnoreEmailSentDate],
[FormattedCV],
[CV],
[DerivedSource],
[IsEmailEngaged],
[IsSMSEngaged]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Stats_Results_JOB_ACI_ACTION_ENGAGED] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JOB_ACI_ACTION_ENGAGED] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [AryaCandidateId],
[Action],
[Engaged]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
/****** Object: Index [Stats_Results_JobId_ACI] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JobId_ACI] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [AryaCandidateId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Stats_Results_JobId_ACI_Action_Engaged] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JobId_ACI_Action_Engaged] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [AryaCandidateId],
[Action],
[Engaged]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Stats_Results_JobId_ACI_DERIVED] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JobId_ACI_DERIVED] ON [dbo].[Results]
(
[JobId] ASC
)
INCLUDE ( [AryaCandidateId],
[DerivedSource]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Stats_Results_JobId_SOURCE_ACI] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JobId_SOURCE_ACI] ON [dbo].[Results]
(
[JobId] ASC,
[Source] ASC
)
INCLUDE ( [AryaCandidateId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [Stats_Results_JobId_Source_ACI_V2] Script Date: 17/10/2018 15:06:18 ******/
CREATE NONCLUSTERED INDEX [Stats_Results_JobId_Source_ACI_V2] ON [dbo].[Results]
(
[JobId] ASC,
[Source] ASC
)
INCLUDE ( [AryaCandidateId]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
ALTER TABLE [dbo].[Results] ADD CONSTRAINT [DF_Results_CreateDate] DEFAULT (getdate()) FOR [CreateDate]
GO
回答1:
I have some suggestions for you to reduce the execution time:
- if the email is empty for the master record, you don't need to run the sub query:
so instead of this statement:
AND NOT EXISTS (
SELECT u.Id FROM Unsubscribe u
WHERE (u.EmailAddress = R.Email OR (u.EmailAddress IS NULL AND R.Email IS NULL))
)
use below statement:
AND (NOT EXISTS (
SELECT u.Id FROM Unsubscribe u
WHERE u.EmailAddress = R.Email )
) or R.Email IS NULL) -- you dont need to check is it is null
- I recommend you to reduce or notation as much as you can, please try to use union instead of OR. You can find some examples in below link:
SQL Performance UNION vs OR
- as I understood you can use JOBID to filter SMTP_Production records, If you can do so:
instead of this statement
AND NOT EXISTS (
SELECT SMTP.Id FROM SMTP_Production SMTP
WHERE SMTP.EmailStatus = 'PICKUP' AND SMTP.CandidateId = R.CandidateId -- can we add SMTP.JobId = R.JobId
)
you can use below
AND NOT EXISTS (
SELECT SMTP.Id FROM SMTP_Production SMTP
WHERE SMTP.EmailStatus = 'PICKUP' AND SMTP.CandidateId = R.CandidateId and SMTP.JobId = R.JobId
)
final version of the query might be like this:
WITH CTE AS
(
SELECT R.Id AS ResultId,
r.JobId,
r.CandidateId,
R.Email,
CAST(0 AS BIT) AS EmailSent,
NULL AS EmailSentDate,
'PICKUP' AS EmailStatus,
GETDATE() AS CreateDate,
C.Id AS UserId,
C.Email AS UserEmail,
NULL AS Subject
FROM RESULTS R
INNER JOIN JOB J ON R.JobId = J.Id
INNER JOIN Consultant C ON J.UserId = C.Id
WHERE
J.DCApproved = 1
AND (J.Closed <> 1)
AND (R.Email <> '' OR R.Email IS NOT NULL)
AND (R.EmailSent <> 1)
AND R.EmailSentDate IS NULL -- email has not been sent
AND (R.EmailStatus = '' OR R.EmailStatus IS NULL)
AND (R.IsEmailSubscribe <> 'False')
-- not already been emailed for this job
AND NOT EXISTS (
SELECT SMTP.Email
FROM SMTP_Production SMTP
WHERE SMTP.JobId = R.JobId AND SMTP.CandidateId = R.CandidateId
)
-- not unsubscribed
AND ((NOT EXISTS (
SELECT u.Id FROM Unsubscribe u
WHERE u.EmailAddress = R.Email )
) or R.Email IS NULL) )
AND NOT EXISTS (
SELECT SMTP.Id FROM SMTP_Production SMTP
WHERE SMTP.EmailStatus = 'PICKUP' AND SMTP.CandidateId = R.CandidateId and SMTP.JobId = R.JobId
)
AND C.Id NOT IN (
-- LIST OF IDS
)
AND J.Id NOT IN (
-- LIST OF IDS
)
AND J.ClientId NOT IN
(
-- LIST OF IDS
)
)
SELECT
CTE.ResultId,
CTE.JobId,
CTE.CandidateId,
CTE.Email,
CTE.EmailSent,
CTE.EmailSentDate,
CTE.EmailStatus,
CTE.CreateDate,
CTE.UserId,
CTE.UserEmail,
NULL
FROM CTE
INNER JOIN
(
SELECT *, row_number() over(partition by CTE.Email, CTE.CandidateId order by CTE.EmailSentDate desc) as rn
FROM CTE
) DCTE ON CTE.ResultId = DCTE.ResultId AND DCTE.rn = 1
来源：https://stackoverflow.com/questions/52856537/sql-long-running-query-maxing-out-server-resource-e-g-ram-cpu