Check if XML nodes are empty in SQL - sql

Question

Hi I am new to XML manipulation, my question would be if there is a possibility of detecting if the XML node is an empty node like this: <gen:nodeName />
I am able to manipulate single nodes however I would be interested if there is an approach like a loop or recursive function that could save some time doing manual labor looking trough every single node. I have no idea how to approach this problem though.
Thanks for help.

Answer 1

You did not specify the dialect of SQL ([sql] is not enough, please specify always the RDBMS incl. version).
This is for SQL-Server, but the semantics should be the same.
DECLARE #xml XML=
N'<root>
<SelfClosing />
<NoContent></NoContent>
<BlankContent> </BlankContent>
<HasContent>blah</HasContent>
<HasContent>other</HasContent>
</root>';
SELECT #xml.query(N'/root/*') AS AnyBelowRoor --All elements
,#xml.query(N'/root/*[text()]') AS AnyWithTextNode --blah and other
,#xml.query(N'/root/*[not(text())]') AS NoText --no text
,#xml.query(N'/root/*[text()="blah"]') AS AnyWithTextNode--blah only
The <SelfClosing /> is semantically the same as the <NoContent><NoContent>. There is no difference.
It might be a surprise, but a blank as content is taken as empty too.
So the check for empty or not empty is the check for the existance of a text() node. one can negate this with not() to find all without a text().
Interesting: The result for NoText comes back as this (SQL-Server)
<SelfClosing />
<NoContent />
<BlankContent />
The three elements are implicitly returned in the shortest format.