Validating individual XML elements in SQL Server 2008R2 - sql-server

Question

I'm writing a stored procedure to process XML data uploaded by the user:
<People>
<Person Id="1" FirstName="..." LastName="..." />
<Person Id="2" FirstName="..." LastName="..." />
<Person Id="3" FirstName="..." LastName="..." />
<Person Id="4" FirstName="..." LastName="..." />
<Person Id="5" FirstName="..." LastName="..." />
</People>
I would like to use a schema to make sure that the entities are valid, but I don't want the entire process to fail just because of one invalid entity. Instead, I would like to log all invalid entities to a table and process the valid entities as normal.
Is there a recommended way to do this?

Answer 1

A pure SQL approach would be:
Create a schema collection that defines <Person>:
CREATE XML SCHEMA COLLECTION [dbo].[testtest] AS
N'<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="Person">
<xs:complexType>
<xs:attribute name="Id" type="xs:int" use="required"/>
<xs:attribute name="FirstName" type="xs:string" use="required"/>
<xs:attribute name="LastName" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
</xs:schema>
'
(one-time operation)
Have an XML query that selects each <Person> node from <People> as a separate row.
Declare a cursor on that query and select each row into an untyped xml variable. After the select, try to assign to a typed xml variable from within a try-catch block.
Resulting code would look like:
declare #source xml = N'
<People>
<Person Id="1" FirstName="..." LastName="..." />
<Person Id="2" FirstName="..." LastName="..." />
<Person Id="f" FirstName="..." LastName="..." />
<Person Id="4" FirstName="..." LastName="..." />
<Person Id="5" FirstName="..." LastName="..." />
</People>';
declare foo cursor
local
forward_only
read_only
for
select t.p.query('.')
from #source.nodes('People/Person') as t(p)
;
declare #x xml (dbo.testtest);
declare #x_raw xml;
open foo;
fetch next from foo into #x_raw;
while ##fetch_status = 0
begin
begin try
set #x = #x_raw;
print cast(#x_raw as nvarchar(max)) + ': OK';
end try
begin catch
print cast(#x_raw as nvarchar(max)) + ': FAILED';
end catch;
fetch next from foo into #x_raw;
end;
close foo;
deallocate foo;
Result:
<Person Id="1" FirstName="..." LastName="..."/>: OK
<Person Id="2" FirstName="..." LastName="..."/>: OK
<Person Id="f" FirstName="..." LastName="..."/>: FAILED
<Person Id="4" FirstName="..." LastName="..."/>: OK
<Person Id="5" FirstName="..." LastName="..."/>: OK
A simpler option is to create a CLR stored procedure that would parse XML in a .NET language.