Is that valid XML and how to replicate with SQL Server - sql-server

Question

I do have to replicate an XML file with SQL Server and I am now stumbling over the following structure inside the XML file and I don't know how to replicate that.
The structure looks like this at the moment for certain tags:
<ART_TAG1>
<UNMLIMITED/>
</ART_TAG1>
<ART_TAG2>
<ART_TAG3>
<Data_Entry/>
</ART_TAG3>
</ART_TAG2>
I am wondering if this is proper XML that the data inside (unlimited and Data_Entry) is enclosed with a closing XML tag. The XML validator https://www.w3schools.com/xml/xml_validator.asp is telling me this is correct. But now I am struggling with replicating that with Transact-SQL.
If I try to replicate that I can only come up with the following TSQL script, which obviously does not fully look like the original.
SELECT 'UNLIMITED' as 'ART_TAG1'
, 'Data_Entry' as 'ART_TAG2/ART_TAG3'
FOR XML PATH(''), ROOT('root')
<root>
<ART_TAG1>UNLIMITED</ART_TAG1>
<ART_TAG2>
<ART_TAG3>Data_Entry</ART_TAG3>
</ART_TAG2>
</root>

Answer 1

If I get this correctly, your question is:
How can I put my query to create those <SomeElement /> tags?
Look at this:
--This will create filled nodes
SELECT 'outer' AS [OuterNode/#attr]
,'inner' AS [OuterNode/InnerNode]
FOR XML PATH('row');
--The empty string is some kind of content
SELECT 'outer' AS [OuterNode/#attr]
,'' AS [OuterNode/InnerNode]
FOR XML PATH('row');
--the missing value (NULL) is omited by default
SELECT 'outer' AS [OuterNode/#attr]
,NULL AS [OuterNode/InnerNode]
FOR XML PATH('row');
--Now check what happens here:
--First XML has an empty element, while the second uses the self-closing element
DECLARE #xml1 XML=
N'<row>
<OuterNode attr="outer">
<InnerNode></InnerNode>
</OuterNode>
</row>';
DECLARE #xml2 XML=
N'<row>
<OuterNode attr="outer">
<InnerNode/>
</OuterNode>
</row>';
SELECT #xml1,#xml2;
The result is the same for both...
Some background: Semantically the empty element <element></element> is exactly the same as the self-closing element <element />. It should not make any difference, whether you use the one or the other. If your consumer cannot deal with this, it is a problem in the reading part.
Yes, you can force any content into XML on string level, but - as the example shows above - this is just a (dangerous) hack.
XML within T-SQL returns - by default - a missing node as NULL and an empty element as empty (depending on the datatype, and beware of the difference between an element and its text() node).
In short: This is nothing you should have to think about...