Select value from XML node where conditions are met - sql-server

Question

I have the following xml which I want to query to turn into a flat table structure.
<RiskBoundReportProcess>
<RiskBoundReport>
<Policy key="Pol126446">
<LineOfBusinessCode>ISR</LineOfBusinessCode>
<AssignedIdentifier>
<RoleCode>Insured</RoleCode>
<Id>BP-1438</Id>
</AssignedIdentifier>
<RiskParticipationPercentIndicator>true</RiskParticipationPercentIndicator>
<PolicySection>
<PolicyProducer>
<RoleCode>Coverholder</RoleCode>
<Producer>
<OrganizationReferences organizationReference="Coverholder"/>
</Producer>
</PolicyProducer>
<PolicyProducer>
<RoleCode>Underwriter</RoleCode>
<Producer>
<Contact>
<PersonReferences>
<PersonName>
<FullName>Name</FullName>
</PersonName>
</PersonReferences>
</Contact>
</Producer>
</PolicyProducer>
<PolicyProducer>
<RoleCode>Broker</RoleCode>
<AssignedIdentifier>
<RoleCode>Broker</RoleCode>
<Id>112</Id>
</AssignedIdentifier>
<Producer>
<OrganizationReferences organizationReference="BrokerOrg112"/>
</Producer>
</PolicyProducer>
<PolicyProducer>
<RoleCode>LondonBroker</RoleCode>
<ProducerReferences producerReference="Binder1">
<ExternalIdentifier>
<TypeCode>UniqueMarketReference</TypeCode>
<Id>UMRGoesHere</Id>
</ExternalIdentifier>
<OrganizationReferences>
<OrganizationName>
<FullName>Partners Ltd</FullName>
</OrganizationName>
</OrganizationReferences>
<BindingAuthorityPeriod>
<StartDate>2014-05-01</StartDate>
<EndDate>2015-04-30</EndDate>
</BindingAuthorityPeriod>
</ProducerReferences>
<RiskParticipationPercent>1.0000</RiskParticipationPercent>
</PolicyProducer>
</PolicySection>
</Policy>
</RiskBoundReport>
</RiskBoundReportProcess>
So far I have two columns. I now want to create a column for UniqueMarketReference which is found in the following node
RiskBoundReportProcess/RiskBoundReport/Policy/PolicySection/PolicyProducer[RoleCode="LondonBroker"]/ProducerReferences/ExternalIdentifier/[TypeCode="UniqueMarketReference"]/Id
How do I modifiy the SQL below to include this?
SELECT
Policy.value('#key', 'VARCHAR(50)') AS PolicyId,
Policy.value('LineOfBusinessCode[1]', 'VARCHAR(50)') AS LineOfBusinessCode
FROM #ACORDXML.nodes('/RiskBoundReportProcess/RiskBoundReport') AS RiskBoundReport(Nodes)
CROSS APPLY RiskBoundReport.Nodes.nodes('Policy') AS Policies(Policy)
I will eventually return The Insured, Coverholer and Underwriter as columns too.

Answer 1

You were very close... The XPath you provided has just one / before [TypeCode ...], which is to much.
Try it like this:
SELECT
Policy.value(N'#key', N'VARCHAR(50)') AS PolicyId
,Policy.value(N'LineOfBusinessCode[1]', N'VARCHAR(50)') AS LineOfBusinessCode
,Policy.value(N'(/RiskBoundReportProcess/RiskBoundReport/Policy/PolicySection
/PolicyProducer[RoleCode="LondonBroker"]
/ProducerReferences/ExternalIdentifier[TypeCode="UniqueMarketReference"]/Id/text())[1]','VARCHAR(50)') AS LondonBroker
,Policy.value(N'(/RiskBoundReportProcess/RiskBoundReport/Policy/PolicySection
/PolicyProducer[RoleCode="Underwriter"]
/Producer/Contact/PersonReferences/PersonName/FullName/text())[1]','VARCHAR(50)') AS Underwriter
FROM #ACORDXML.nodes('/RiskBoundReportProcess/RiskBoundReport') AS RiskBoundReport(Nodes)
CROSS APPLY RiskBoundReport.Nodes.nodes('Policy') AS Policies(Policy);
Some of your nodes look like 1:n-related (<PersonReferences><PersonName>...). This might need some extra effort (.nodes())...