SQL Server：如何获取指定属性的 XML 元素的值？

Question

For the usage in a SQL query I need to get the value of a specific XML element. The XML element is specified by its attribute.

My XML elements looks like this:

<translations>
  <value lang="en-US">example</value>
  <value lang="de-DE">Beispiel</value>
</translations>

and the value I am looking for would be "example" when I specify lang to be "en-US".

I found a way to get this value by using the query() function and afterwards the value() function.

declare @S varchar(max)

set @S =
'<translations>
  <value lang="en-US">example</value>
  <value lang="de-DE">Beispiel</value>
</translations>'

declare @X xml

set @X = CAST(@S as xml)

select @X.query('/translations/value[@lang="en-US"]').value('.','varchar(max)')

This select statement return the value "example" I am looking for by using the query() and value() function. But is there also a - more convenient - way to only use value() OR query()?

Thank you in advance!

Answer 1

Sure there is...

You also can shorten the declaration:

declare @X xml=
'<translations>
  <value lang="en-US">example</value>
  <value lang="de-DE">Beispiel</value>
</translations>';

select @X.value('(/translations/value[@lang="en-US"])[1]','varchar(max)');

The point is, that you need a singleton result when you are using .value() . You achieve this by putting the XPath in paranthesis and force the first element to be taken (in this case it's the only element).

Btw: If you need this (and sooner or later you will need this...), you might put the "en-US" as parameter into your query like this:

declare @prm VARCHAR(10)='en_US';
select @X.value('(/translations/value[@lang=sql:variable("@prm")])[1]','varchar(max)');

You can reach the similar, but with a value of the actual query by using sql:column() .