Xml with null Column

How to get null value from XML column.

XML requirements

XML tags are case sensitive. Opening and closing tags must be written with the same case
In XML, all elements must be properly nested within each other
In XML, the attribute values must always be quoted
“xsi:nil” represents the null value in XML

<message>salary &lt; 1000</message>
&lt;	<	less than
&gt;	>	greater than
&amp;	&	ampersand 
&apos;	'	apostrophe
&quot;	"	quotation mark

select name, object_id,principal_id from sys.tables for XML PATH, ELEMENTS XSINIL;

<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_db</name>
  <object_id>117575457</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_dev</name>
  <object_id>133575514</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_usg</name>
  <object_id>149575571</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_monitor</name>
  <object_id>1803153469</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>MSreplication_options</name>
  <object_id>2107154552</object_id>
  <principal_id xsi:nil="true" />
</row>

declare @xml xml
select @xml = N'<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_db</name>
  <object_id>117575457</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_dev</name>
  <object_id>133575514</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_fallback_usg</name>
  <object_id>149575571</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>spt_monitor</name>
  <object_id>1803153469</object_id>
  <principal_id xsi:nil="true" />
</row>
<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <name>MSreplication_options</name>
  <object_id>2107154552</object_id>
  <principal_id xsi:nil="true" />
</row>'
;with xmlnamespaces('http://www.w3.org/2001/XMLSchema-instance' as xsi)
select  N.C.value('object_id[1]', 'int') as object_id
,N.C.value('principal_id[1][not(@xsi:nil = "true")]', 'int') as principal_id
,N.C.value('name[1]', 'varchar(100)') as name
from @xml.nodes('//row') N(C)

Other Reference:

How to work with xml type using Query