Merging Multiple Rows into a single Row

Question

I've read a number of posts with no real good answers or answers that might be good for tables with 3 columns of data. I have a table with 33 columns that will all need to be combined. A little history. Apparently in production the Primary Key Constraint
was dropped which allowed some duplicate data into the table. Now they want me to squish the records together to fix it.
Sorry I couldn't include the screen shot of the data, MSDN says my account isn't verified...
My requirements when I'm putting them together, CERElibilityID is a unique column. This is a sticky problem because in the related tables it is only one of the parent records gets child records related to it.
 I just want to keep the one that has the child records in CERPrepActivity table. If there are no child records then the rule will be like all the other records with data. 
If a  field is null and another record has data we take the record that has data.
If multiple records have data we take the record that has the highest "ModifiedOn" timestamp column value.
I feel like I'm asking a lot, but I'm in a bit of a bind and I've spent the morning Googling and have come up with nothing 
Thank  you for any help the community can provide and the more specific you can be the better. I'm not a DBA or SQL guru by any stretch so I'm way out of my element.
Thanks

Answer 1

Using the systables, you can get information about your table. I put these together:
SELECT '
LEFT OUTER JOIN #CEREligibility ['+c.name+']
ON s.caseID = ['+c.name+'].caseID
AND s.modifiedOn = ['+c.name+'].modifiedOn
AND ['+c.name+'].['+c.name+'] = (SELECT TOP 1 ['+c.name+'] FROM #CEREligibility WHERE caseID = s.caseID AND ['+c.name+'] IS NOT NULL ORDER BY ModifiedOn)
AND ['+c.name+'].['+c.name+'] IS NOT NULL'
FROM tempdb.sys.objects o
INNER JOIN tempdb.sys.columns c
ON o.object_id = c.object_id
AND o.name LIKE '#CEREligibility%'
SELECT '['+c.name+'].['+c.name+'] AS ['+c.name+'], '
FROM tempdb.sys.objects o
INNER JOIN tempdb.sys.columns c
ON o.object_id = c.object_id
AND o.name LIKE '#CEREligibility%'
On my test system I created your table as a temp table named #CEREligibility.
The first of these two queries generates LEFT OUT JOIN SQL for a self join. Because we're using the columns systable, a LOJ for each column is generated.
The second, produces a select list.
Putting the two together like so, and adding a FROM and GROUP BY gives us:
SELECT
MAX([CEREligibilityId].[CEREligibilityId]) AS [CEREligibilityId], s.[CaseId], MAX([M2Eligibility].[M2Eligibility]) AS [M2Eligibility], MAX([CDREligibility].[CDREligibility]) AS [CDREligibility], MAX([M2Comments].[M2Comments]) AS [M2Comments], MAX([M2CommentsRtf].[M2CommentsRtf]) AS [M2CommentsRtf], MAX([CDRComments].[CDRComments]) AS [CDRComments], MAX([CDRCommentsRtf].[CDRCommentsRtf]) AS [CDRCommentsRtf], MAX([RIAWA].[RIAWA]) AS [RIAWA], MAX([RIAWADate].[RIAWADate]) AS [RIAWADate], MAX([EducationAndTraining].[EducationAndTraining]) AS [EducationAndTraining], MAX([EducationAndTrainingDate].[EducationAndTrainingDate]) AS [EducationAndTrainingDate], MAX([Internship].[Internship]) AS [Internship], MAX([InternshipDate].[InternshipDate]) AS [InternshipDate], MAX([Apprenticeship].[Apprenticeship]) AS [Apprenticeship], MAX([ApprenticeshipDate].[ApprenticeshipDate]) AS [ApprenticeshipDate], MAX([Entrepreneurship].[Entrepreneurship]) AS [Entrepreneurship], MAX([EntrepreneurshipDate].[EntrepreneurshipDate]) AS [EntrepreneurshipDate], MAX([EmploymentPrep].[EmploymentPrep]) AS [EmploymentPrep], MAX([EmploymentPrepDate].[EmploymentPrepDate]) AS [EmploymentPrepDate], MAX([OTPrep].[OTPrep]) AS [OTPrep], MAX([OTPrepDate].[OTPrepDate]) AS [OTPrepDate], MAX([ExitInterview].[ExitInterview]) AS [ExitInterview], MAX([ExitInterviewDate].[ExitInterviewDate]) AS [ExitInterviewDate], MAX([CreatedOn].[CreatedOn]) AS [CreatedOn], MAX([CreatedBy].[CreatedBy]) AS [CreatedBy], MAX([ModifiedOn].[ModifiedOn]) AS [ModifiedOn], MAX([ModifiedBy].[ModifiedBy]) AS [ModifiedBy], MAX([BCPermInEligibility].[BCPermInEligibility]) AS [BCPermInEligibility], MAX([CCPermInEligibility].[CCPermInEligibility]) AS [CCPermInEligibility], MAX([M2EligibilityDate].[M2EligibilityDate]) AS [M2EligibilityDate], MAX([CDREligibilityDate].[CDREligibilityDate]) AS [CDREligibilityDate], MAX([ExitSeparationCode].[ExitSeparationCode]) AS [ExitSeparationCode], MAX([ExitSeparationSubCode].[ExitSeparationSubCode]) AS [ExitSeparationSubCode]
FROM #CEREligibility s
LEFT OUTER JOIN #CEREligibility [CEREligibilityId]
ON s.caseID = [CEREligibilityId].caseID
AND s.modifiedOn = [CEREligibilityId].modifiedOn
AND [CEREligibilityId].[CEREligibilityId] = (SELECT TOP 1 [CEREligibilityId] FROM #CEREligibility WHERE caseID = s.caseID AND [CEREligibilityId] IS NOT NULL ORDER BY ModifiedOn)
AND [CEREligibilityId].[CEREligibilityId] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CaseId]
ON s.caseID = [CaseId].caseID
AND s.modifiedOn = [CaseId].modifiedOn
AND [CaseId].[CaseId] = (SELECT TOP 1 [CaseId] FROM #CEREligibility WHERE caseID = s.caseID AND [CaseId] IS NOT NULL ORDER BY ModifiedOn)
AND [CaseId].[CaseId] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [M2Eligibility]
ON s.caseID = [M2Eligibility].caseID
AND s.modifiedOn = [M2Eligibility].modifiedOn
AND [M2Eligibility].[M2Eligibility] = (SELECT TOP 1 [M2Eligibility] FROM #CEREligibility WHERE caseID = s.caseID AND [M2Eligibility] IS NOT NULL ORDER BY ModifiedOn)
AND [M2Eligibility].[M2Eligibility] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CDREligibility]
ON s.caseID = [CDREligibility].caseID
AND s.modifiedOn = [CDREligibility].modifiedOn
AND [CDREligibility].[CDREligibility] = (SELECT TOP 1 [CDREligibility] FROM #CEREligibility WHERE caseID = s.caseID AND [CDREligibility] IS NOT NULL ORDER BY ModifiedOn)
AND [CDREligibility].[CDREligibility] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [M2Comments]
ON s.caseID = [M2Comments].caseID
AND s.modifiedOn = [M2Comments].modifiedOn
AND [M2Comments].[M2Comments] = (SELECT TOP 1 [M2Comments] FROM #CEREligibility WHERE caseID = s.caseID AND [M2Comments] IS NOT NULL ORDER BY ModifiedOn)
AND [M2Comments].[M2Comments] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [M2CommentsRtf]
ON s.caseID = [M2CommentsRtf].caseID
AND s.modifiedOn = [M2CommentsRtf].modifiedOn
AND [M2CommentsRtf].[M2CommentsRtf] = (SELECT TOP 1 [M2CommentsRtf] FROM #CEREligibility WHERE caseID = s.caseID AND [M2CommentsRtf] IS NOT NULL ORDER BY ModifiedOn)
AND [M2CommentsRtf].[M2CommentsRtf] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CDRComments]
ON s.caseID = [CDRComments].caseID
AND s.modifiedOn = [CDRComments].modifiedOn
AND [CDRComments].[CDRComments] = (SELECT TOP 1 [CDRComments] FROM #CEREligibility WHERE caseID = s.caseID AND [CDRComments] IS NOT NULL ORDER BY ModifiedOn)
AND [CDRComments].[CDRComments] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CDRCommentsRtf]
ON s.caseID = [CDRCommentsRtf].caseID
AND s.modifiedOn = [CDRCommentsRtf].modifiedOn
AND [CDRCommentsRtf].[CDRCommentsRtf] = (SELECT TOP 1 [CDRCommentsRtf] FROM #CEREligibility WHERE caseID = s.caseID AND [CDRCommentsRtf] IS NOT NULL ORDER BY ModifiedOn)
AND [CDRCommentsRtf].[CDRCommentsRtf] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [RIAWA]
ON s.caseID = [RIAWA].caseID
AND s.modifiedOn = [RIAWA].modifiedOn
AND [RIAWA].[RIAWA] = (SELECT TOP 1 [RIAWA] FROM #CEREligibility WHERE caseID = s.caseID AND [RIAWA] IS NOT NULL ORDER BY ModifiedOn)
AND [RIAWA].[RIAWA] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [RIAWADate]
ON s.caseID = [RIAWADate].caseID
AND s.modifiedOn = [RIAWADate].modifiedOn
AND [RIAWADate].[RIAWADate] = (SELECT TOP 1 [RIAWADate] FROM #CEREligibility WHERE caseID = s.caseID AND [RIAWADate] IS NOT NULL ORDER BY ModifiedOn)
AND [RIAWADate].[RIAWADate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [EducationAndTraining]
ON s.caseID = [EducationAndTraining].caseID
AND s.modifiedOn = [EducationAndTraining].modifiedOn
AND [EducationAndTraining].[EducationAndTraining] = (SELECT TOP 1 [EducationAndTraining] FROM #CEREligibility WHERE caseID = s.caseID AND [EducationAndTraining] IS NOT NULL ORDER BY ModifiedOn)
AND [EducationAndTraining].[EducationAndTraining] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [EducationAndTrainingDate]
ON s.caseID = [EducationAndTrainingDate].caseID
AND s.modifiedOn = [EducationAndTrainingDate].modifiedOn
AND [EducationAndTrainingDate].[EducationAndTrainingDate] = (SELECT TOP 1 [EducationAndTrainingDate] FROM #CEREligibility WHERE caseID = s.caseID AND [EducationAndTrainingDate] IS NOT NULL ORDER BY ModifiedOn)
AND [EducationAndTrainingDate].[EducationAndTrainingDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [Internship]
ON s.caseID = [Internship].caseID
AND s.modifiedOn = [Internship].modifiedOn
AND [Internship].[Internship] = (SELECT TOP 1 [Internship] FROM #CEREligibility WHERE caseID = s.caseID AND [Internship] IS NOT NULL ORDER BY ModifiedOn)
AND [Internship].[Internship] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [InternshipDate]
ON s.caseID = [InternshipDate].caseID
AND s.modifiedOn = [InternshipDate].modifiedOn
AND [InternshipDate].[InternshipDate] = (SELECT TOP 1 [InternshipDate] FROM #CEREligibility WHERE caseID = s.caseID AND [InternshipDate] IS NOT NULL ORDER BY ModifiedOn)
AND [InternshipDate].[InternshipDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [Apprenticeship]
ON s.caseID = [Apprenticeship].caseID
AND s.modifiedOn = [Apprenticeship].modifiedOn
AND [Apprenticeship].[Apprenticeship] = (SELECT TOP 1 [Apprenticeship] FROM #CEREligibility WHERE caseID = s.caseID AND [Apprenticeship] IS NOT NULL ORDER BY ModifiedOn)
AND [Apprenticeship].[Apprenticeship] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ApprenticeshipDate]
ON s.caseID = [ApprenticeshipDate].caseID
AND s.modifiedOn = [ApprenticeshipDate].modifiedOn
AND [ApprenticeshipDate].[ApprenticeshipDate] = (SELECT TOP 1 [ApprenticeshipDate] FROM #CEREligibility WHERE caseID = s.caseID AND [ApprenticeshipDate] IS NOT NULL ORDER BY ModifiedOn)
AND [ApprenticeshipDate].[ApprenticeshipDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [Entrepreneurship]
ON s.caseID = [Entrepreneurship].caseID
AND s.modifiedOn = [Entrepreneurship].modifiedOn
AND [Entrepreneurship].[Entrepreneurship] = (SELECT TOP 1 [Entrepreneurship] FROM #CEREligibility WHERE caseID = s.caseID AND [Entrepreneurship] IS NOT NULL ORDER BY ModifiedOn)
AND [Entrepreneurship].[Entrepreneurship] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [EntrepreneurshipDate]
ON s.caseID = [EntrepreneurshipDate].caseID
AND s.modifiedOn = [EntrepreneurshipDate].modifiedOn
AND [EntrepreneurshipDate].[EntrepreneurshipDate] = (SELECT TOP 1 [EntrepreneurshipDate] FROM #CEREligibility WHERE caseID = s.caseID AND [EntrepreneurshipDate] IS NOT NULL ORDER BY ModifiedOn)
AND [EntrepreneurshipDate].[EntrepreneurshipDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [EmploymentPrep]
ON s.caseID = [EmploymentPrep].caseID
AND s.modifiedOn = [EmploymentPrep].modifiedOn
AND [EmploymentPrep].[EmploymentPrep] = (SELECT TOP 1 [EmploymentPrep] FROM #CEREligibility WHERE caseID = s.caseID AND [EmploymentPrep] IS NOT NULL ORDER BY ModifiedOn)
AND [EmploymentPrep].[EmploymentPrep] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [EmploymentPrepDate]
ON s.caseID = [EmploymentPrepDate].caseID
AND s.modifiedOn = [EmploymentPrepDate].modifiedOn
AND [EmploymentPrepDate].[EmploymentPrepDate] = (SELECT TOP 1 [EmploymentPrepDate] FROM #CEREligibility WHERE caseID = s.caseID AND [EmploymentPrepDate] IS NOT NULL ORDER BY ModifiedOn)
AND [EmploymentPrepDate].[EmploymentPrepDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [OTPrep]
ON s.caseID = [OTPrep].caseID
AND s.modifiedOn = [OTPrep].modifiedOn
AND [OTPrep].[OTPrep] = (SELECT TOP 1 [OTPrep] FROM #CEREligibility WHERE caseID = s.caseID AND [OTPrep] IS NOT NULL ORDER BY ModifiedOn)
AND [OTPrep].[OTPrep] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [OTPrepDate]
ON s.caseID = [OTPrepDate].caseID
AND s.modifiedOn = [OTPrepDate].modifiedOn
AND [OTPrepDate].[OTPrepDate] = (SELECT TOP 1 [OTPrepDate] FROM #CEREligibility WHERE caseID = s.caseID AND [OTPrepDate] IS NOT NULL ORDER BY ModifiedOn)
AND [OTPrepDate].[OTPrepDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ExitInterview]
ON s.caseID = [ExitInterview].caseID
AND s.modifiedOn = [ExitInterview].modifiedOn
AND [ExitInterview].[ExitInterview] = (SELECT TOP 1 [ExitInterview] FROM #CEREligibility WHERE caseID = s.caseID AND [ExitInterview] IS NOT NULL ORDER BY ModifiedOn)
AND [ExitInterview].[ExitInterview] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ExitInterviewDate]
ON s.caseID = [ExitInterviewDate].caseID
AND s.modifiedOn = [ExitInterviewDate].modifiedOn
AND [ExitInterviewDate].[ExitInterviewDate] = (SELECT TOP 1 [ExitInterviewDate] FROM #CEREligibility WHERE caseID = s.caseID AND [ExitInterviewDate] IS NOT NULL ORDER BY ModifiedOn)
AND [ExitInterviewDate].[ExitInterviewDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CreatedOn]
ON s.caseID = [CreatedOn].caseID
AND s.modifiedOn = [CreatedOn].modifiedOn
AND [CreatedOn].[CreatedOn] = (SELECT TOP 1 [CreatedOn] FROM #CEREligibility WHERE caseID = s.caseID AND [CreatedOn] IS NOT NULL ORDER BY ModifiedOn)
AND [CreatedOn].[CreatedOn] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CreatedBy]
ON s.caseID = [CreatedBy].caseID
AND s.modifiedOn = [CreatedBy].modifiedOn
AND [CreatedBy].[CreatedBy] = (SELECT TOP 1 [CreatedBy] FROM #CEREligibility WHERE caseID = s.caseID AND [CreatedBy] IS NOT NULL ORDER BY ModifiedOn)
AND [CreatedBy].[CreatedBy] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ModifiedOn]
ON s.caseID = [ModifiedOn].caseID
AND s.modifiedOn = [ModifiedOn].modifiedOn
AND [ModifiedOn].[ModifiedOn] = (SELECT TOP 1 [ModifiedOn] FROM #CEREligibility WHERE caseID = s.caseID AND [ModifiedOn] IS NOT NULL ORDER BY ModifiedOn)
AND [ModifiedOn].[ModifiedOn] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ModifiedBy]
ON s.caseID = [ModifiedBy].caseID
AND s.modifiedOn = [ModifiedBy].modifiedOn
AND [ModifiedBy].[ModifiedBy] = (SELECT TOP 1 [ModifiedBy] FROM #CEREligibility WHERE caseID = s.caseID AND [ModifiedBy] IS NOT NULL ORDER BY ModifiedOn)
AND [ModifiedBy].[ModifiedBy] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [BCPermInEligibility]
ON s.caseID = [BCPermInEligibility].caseID
AND s.modifiedOn = [BCPermInEligibility].modifiedOn
AND [BCPermInEligibility].[BCPermInEligibility] = (SELECT TOP 1 [BCPermInEligibility] FROM #CEREligibility WHERE caseID = s.caseID AND [BCPermInEligibility] IS NOT NULL ORDER BY ModifiedOn)
AND [BCPermInEligibility].[BCPermInEligibility] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CCPermInEligibility]
ON s.caseID = [CCPermInEligibility].caseID
AND s.modifiedOn = [CCPermInEligibility].modifiedOn
AND [CCPermInEligibility].[CCPermInEligibility] = (SELECT TOP 1 [CCPermInEligibility] FROM #CEREligibility WHERE caseID = s.caseID AND [CCPermInEligibility] IS NOT NULL ORDER BY ModifiedOn)
AND [CCPermInEligibility].[CCPermInEligibility] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [M2EligibilityDate]
ON s.caseID = [M2EligibilityDate].caseID
AND s.modifiedOn = [M2EligibilityDate].modifiedOn
AND [M2EligibilityDate].[M2EligibilityDate] = (SELECT TOP 1 [M2EligibilityDate] FROM #CEREligibility WHERE caseID = s.caseID AND [M2EligibilityDate] IS NOT NULL ORDER BY ModifiedOn)
AND [M2EligibilityDate].[M2EligibilityDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [CDREligibilityDate]
ON s.caseID = [CDREligibilityDate].caseID
AND s.modifiedOn = [CDREligibilityDate].modifiedOn
AND [CDREligibilityDate].[CDREligibilityDate] = (SELECT TOP 1 [CDREligibilityDate] FROM #CEREligibility WHERE caseID = s.caseID AND [CDREligibilityDate] IS NOT NULL ORDER BY ModifiedOn)
AND [CDREligibilityDate].[CDREligibilityDate] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ExitSeparationCode]
ON s.caseID = [ExitSeparationCode].caseID
AND s.modifiedOn = [ExitSeparationCode].modifiedOn
AND [ExitSeparationCode].[ExitSeparationCode] = (SELECT TOP 1 [ExitSeparationCode] FROM #CEREligibility WHERE caseID = s.caseID AND [ExitSeparationCode] IS NOT NULL ORDER BY ModifiedOn)
AND [ExitSeparationCode].[ExitSeparationCode] IS NOT NULL
LEFT OUTER JOIN #CEREligibility [ExitSeparationSubCode]
ON s.caseID = [ExitSeparationSubCode].caseID
AND s.modifiedOn = [ExitSeparationSubCode].modifiedOn
AND [ExitSeparationSubCode].[ExitSeparationSubCode] = (SELECT TOP 1 [ExitSeparationSubCode] FROM #CEREligibility WHERE caseID = s.caseID AND [ExitSeparationSubCode] IS NOT NULL ORDER BY ModifiedOn)
AND [ExitSeparationSubCode].[ExitSeparationSubCode] IS NOT NULL
GROUP BY s.caseID
When I ran this against your test data, It produced a single row for each of the two case ID's.
To keep performance in line, I also created a covering index on the temp table:
CREATE INDEX idx_caseID_ModifiedOn ON #CEREligibility (caseID, modifiedOn) INCLUDE ([CEREligibilityId], [M2Eligibility], [CDREligibility], [M2Comments], [M2CommentsRtf], [CDRComments], [CDRCommentsRtf], [RIAWA], [RIAWADate], [EducationAndTraining], [EducationAndTrainingDate], [Internship], [InternshipDate], [Apprenticeship], [ApprenticeshipDate], [Entrepreneurship], [EntrepreneurshipDate], [EmploymentPrep], [EmploymentPrepDate], [OTPrep], [OTPrepDate], [ExitInterview], [ExitInterviewDate], [CreatedOn], [CreatedBy], [ModifiedBy], [BCPermInEligibility], [CCPermInEligibility], [M2EligibilityDate], [CDREligibilityDate], [ExitSeparationCode], [ExitSeparationSubCode])
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