The string '' is not a valid XsdDateTime value

Question

I have the TSQL code displayed below, trying to generate the following XML:
<Provider xmlns="http://www.tn.gov/mental/Schemas/CrisisAssessment" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.tn.gov/mental/Schemas/CrisisAssessment">
<NPI>1306875695</NPI>
<FileCreationDate>2014-01-31</FileCreationDate>
<FileCreationTime>10:51:03</FileCreationTime>
<Patient>
<ProviderPatientNo>190366</ProviderPatientNo>
<LastName>Gi</LastName>
<FirstName>Brandon</FirstName>
<PhoneAssessment>
<ProviderPhoneAssessmentId>4F2E4674-FDB5-4D8F-8D9C-01AFF9DFA3A1</ProviderPhoneAssessmentId>
<F2FAssessment>
<ProviderF2FAssessmentId>D0A5A65B-3F30-47A4-A350-AE3CBC68DA25</ProviderF2FAssessmentId>
<DateTransportedToFacility xsi:nil="true" />
<TimeTransportedToFacility xsi:nil="true" />
<FollowupContacted>0</FollowupContacted>
</F2FAssessment>
</PhoneAssessment>
</Patient>
</Provider>
But instead this looks like:
<Provider xmlns="http://www.tn.gov/mental/Schemas/CrisisAssessment" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.tn.gov/mental/Schemas/CrisisAssessment">
<NPI>1306875695</NPI>
<FileCreationDate>2014-01-31</FileCreationDate>
<FileCreationTime>10:51:03</FileCreationTime>
<Patient>
<ProviderPatientNo>190366</ProviderPatientNo>
<LastName>Gi</LastName>
<FirstName>Brandon</FirstName>
<PhoneAssessment>
<ProviderPhoneAssessmentId>4F2E4674-FDB5-4D8F-8D9C-01AFF9DFA3A1</ProviderPhoneAssessmentId>
<F2FAssessment>
<ProviderF2FAssessmentId>D0A5A65B-3F30-47A4-A350-AE3CBC68DA25</ProviderF2FAssessmentId>
<DateTransportedToFacility />
<TimeTransportedToFacility />
<FollowupContacted>0</FollowupContacted>
</F2FAssessment>
</PhoneAssessment>
</Patient>
</Provider>
This is the TSQL code for this:
; with prov as (
select NPI,FileCreationDate, FileCreationTime
from July2013_Import_Final
group by NPI,FileCreationDate, FileCreationTime
SELECT
NPI as [NPI],
FileCreationDate as [FileCreationDate],
FileCreationTime as [FileCreationTime],
Select
ProviderPatientNo ,
LastName as [LastName],
FirstName as [FirstName],
Select
t_phone.ProviderPhoneAssessmentId,
t_assess.ProviderF2FAssessmentId as [F2FAssessment/ProviderF2FAssessmentId],
[DateTransportedToFacility] as [F2FAssessment/DateTransportedToFacility],
TimeTransportedToFacility AS [F2FAssessment/TimeTransportedToFacility]
FollowupContacted AS [F2FAssessment/FollowupContacted]
FROM (select distinct ProviderPatientNo, ProviderPhoneAssessmentId,ProviderF2FAssessmentId
from #phones where CallDisposition in (1,5,8) and ProviderPhoneAssessmentId = t_base.ProviderPhoneAssessmentId) t_phone
inner join #Assessments t_assess On t_phone.ProviderPatientNo = t_assess.ProviderPatientNo and t_assess.ProviderF2FAssessmentId is not null
left join #Drugs d on d.ProviderF2FAssessmentId = t_assess.ProviderF2FAssessmentId
left join #HospAlt ha on ha.ProviderF2FAssessmentId = t_assess.ProviderF2FAssessmentId
left join #HospDisp hd on hd.ProviderF2FAssessmentId = t_assess.ProviderF2FAssessmentId
--where t_phone.ProviderPatientNo = '00200791'
FOR XML PATH('PhoneAssessment'), ELEMENTS, type) AS [*]
FROM (select distinct ProviderPhoneAssessmentId, ProviderPatientNo,LastName,FirstName,SSN,DOB,Gender,Race,Ethnicity from #base
) t_base
FOR XML PATH('Patient'), type
from prov
for xml path(''), root('Provider')
And I don't want to use the code:
FOR XML PATH('PhoneAssessment'), ELEMENTS XSINIL, TYPE)
Because I don't want this behavior for all elements.  How can I modify my SQL query?
Ryan D

Answer 1

I see it very quickly when you point it out.  Without your note, it would have taken a good five minutes of painstaking node by node comparison.
What is the data type of these two columns?  The xml that is produced is like it is a varchar that is empty string. 
I will assume that these are varchar.  Add the following bits (I have added the full namespace declaration as part of your with clause):
; with xmlnamespaces (
default 'http://www.tn.gov/mental/Schemas/CrisisAssessment'
, 'http://www.w3.org/2001/XMLSchema-instance' as xsi)
, prov as (
case when isnull([DateTransportedToFacility], '') = ''
then 'true' else null end as [F2FAssessment/DateTransportedToFacility/@xsi:nil],
[DateTransportedToFacility] as [F2FAssessment/DateTransportedToFacility/*],
case when isnull([TimeTransportedToFacility], '') = ''
then 'true' else null end as
[F2FAssessment/TimeTransportedToFacility/@xsi:nil],
TimeTransportedToFacility AS [F2FAssessment/TimeTransportedToFacility/*]
Russel Loski, MCT, MCSE Data Platform/Business Intelligence. Twitter: @sqlmovers; blog: www.sqlmovers.com