Can't figure out how to search XML column in my table - sql-server

Question

I have a table called v_EpisodeAudit, with a column called EventData that contains XML data. The XML data differs from row to row, so one record could have XML data in this column that looks like this:
<AddMDMDocument>
<EpisodeMDMId>282521</EpisodeMDMId>
<OncologyReferral>0</OncologyReferral>
<SpecialPalliativeReferral>0</SpecialPalliativeReferral>
<SurgeonReferral>0</SurgeonReferral>
<MDMReport>0</MDMReport>
<GPReferral>0</GPReferral>
<GPReferralApproval>0</GPReferralApproval>
<GeneralPalliativeCare>0</GeneralPalliativeCare>
<AuditLogin>mkell010</AuditLogin>
<AuditTrust>4</AuditTrust>
<Error />
</AddMDMDocument>
while another row might contain the following XML data:
<CloseEpisode>
<EpisodeId>652503</EpisodeId>
<TrackingStatusId>9</TrackingStatusId>
<TrackingClosureReason>100</TrackingClosureReason>
<DateOfTrackingClosure>Sep 25 2017 12:37PM</DateOfTrackingClosure>
<AuditLogin>ccass001</AuditLogin>
<AuditTrust>1</AuditTrust>
<Error />
</CloseEpisode>
And there are further differing types/configurations of XML data. I've read about 20 different sources this morning trying to work out how to search against the XML data in this column to get a specific EpisodeId in the CloseEpisode XMLs, and I can't for the life of me figure it out. Can anyone help me with a query that will find a specified EpisodeId in this column?

Answer 1

XML can be queried very generically. Some approaches:
DECLARE #v_EpisodeAudit TABLE(ID INT IDENTITY, [EventData] XML);
INSERT INTO #v_EpisodeAudit VALUES
(N'<AddMDMDocument>
<EpisodeMDMId>282521</EpisodeMDMId>
<OncologyReferral>0</OncologyReferral>
<SpecialPalliativeReferral>0</SpecialPalliativeReferral>
<SurgeonReferral>0</SurgeonReferral>
<MDMReport>0</MDMReport>
<GPReferral>0</GPReferral>
<GPReferralApproval>0</GPReferralApproval>
<GeneralPalliativeCare>0</GeneralPalliativeCare>
<AuditLogin>mkell010</AuditLogin>
<AuditTrust>4</AuditTrust>
<Error />
</AddMDMDocument>')
,(N'<CloseEpisode>
<EpisodeId>652503</EpisodeId>
<TrackingStatusId>9</TrackingStatusId>
<TrackingClosureReason>100</TrackingClosureReason>
<DateOfTrackingClosure>Sep 25 2017 12:37PM</DateOfTrackingClosure>
<AuditLogin>ccass001</AuditLogin>
<AuditTrust>1</AuditTrust>
<Error />
</CloseEpisode>');00
--This will return the very first node on the second level
SELECT ID
,vEA.[EventData].value(N'local-name(/*[1]/*[1])',N'nvarchar(max)') AS NodeName
,vEA.[EventData].value(N'/*[1]/*[1]/text()[1]',N'nvarchar(max)') AS NodeValue
FROM #v_EpisodeAudit AS vEA
--This will return all nodes of the sevond level and use WHERE with LIKE to find the Episode..Id elements
SELECT ID
,SecondLevelNode.Nd.value(N'local-name(.)',N'nvarchar(max)') AS NodeName
,SecondLevelNode.Nd.value(N'text()[1]',N'nvarchar(max)') AS NodeValue
FROM #v_EpisodeAudit AS vEA
OUTER APPLY vEA.[EventData].nodes(N'/*/*') AS SecondLevelNode(Nd)
WHERE SecondLevelNode.Nd.value(N'local-name(.)',N'nvarchar(max)') LIKE 'Episode%' --or LIKE 'Episode%Id'
--Similar but filtering on XQuery level
SELECT ID
,SecondLevelNode.Nd.value(N'local-name(.)',N'nvarchar(max)') AS NodeName
,SecondLevelNode.Nd.value(N'text()[1]',N'nvarchar(max)') AS NodeValue
FROM #v_EpisodeAudit AS vEA
OUTER APPLY vEA.[EventData].nodes(N'/*/*[substring(local-name(),1,7)="Episode"]') AS SecondLevelNode(Nd)

Answer 2

Use the xml querying functions
select EventData.value('(/CloseEpisode/EpisodeId)[1]','int')
from v_EpisodeAudit
where EventData.value('local-name(/*[1])','varchar(100)')='CloseEpisode'
or perhaps
select EventData
from #v_EpisodeAudit
where EventData.value('(/CloseEpisode/EpisodeId)[1]','int')=652503
depending on what you're trying to do.
If you don't know the root node name, you could use
select EventData.value('(//EpisodeId)[1]','int')
from v_EpisodeAudit
where EventData.exist('//EpisodeId')=1
See https://learn.microsoft.com/en-us/sql/t-sql/xml/value-method-xml-data-type