如何从节点获取价值？ SQL Server XML dml

Question

@x xml:'
<a number="1">
 <b>1</b>
</a>'

I want use query() to get value (can't use value() )

@x.query('string(/a[1]/b[1])') 

is ok.

@x.query('string(/a[@number="1"]/b)') 

throws an error.

Do you have any solution? I want use [@number="1"] to get value.

Answer 1

你可以试试这个。

@x.query('string( (/a[@number="1"]/b)[1])') 

Answer 2

In most cases one wants to read more than one value from a given node. You can use a combination of .nodes() (very related to .query() , but returning a derived table) and .query() or .value() like here:

DECLARE @x xml=
N'<a number="1">
 <b>1</b>
</a>';

SELECT MyA.value(N'(b/text())[1]','int') AS ReadTheValue
      ,MyA.query(N'b') QueryTheValue
FROM @x.nodes(N'/a[@number="1"]') AS A(MyA); 

You can pass in the search value as a variable like here:

DECLARE @SearchNumber INT=1;
SELECT MyA.value(N'(b/text())[1]','int') AS ReadTheValue
      ,MyA.query(N'b') QueryTheValue
FROM @x.nodes(N'/a[@number=sql:variable("@SearchNumber")]') AS A(MyA); 

If you need nothing else then the value through .query() go with the solution provided by Serkan Aslan. You were just missing to ensure the inner experession to be singleton.

But I must admit, that I have no idea, why one should need this...