sql-server - Xpath query on name rather than index

Question

I have the following xml in an xml column in sql server, it is in a table along with a id column -

<ArrayOfExtVar xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <ExtVar>
    <Name xsi:type="xsd:string">Rate Code</Name>
    <Value xsi:type="xsd:string">E46</Value>
  </ExtVar>
  <ExtVar>
    <Name xsi:type="xsd:string">Middle Name</Name>
    <Value xsi:type="xsd:string">Henry</Value>
  </ExtVar>
</ArrayOfExtVar>

And I have the following XPath -

SELECT CustID, 
ExtVars.value('(/ArrayOfExtVar/ExtVar/Value)[1]', 'Nvarchar(max)') AS RateCode,
ExtVars.value('(/ArrayOfExtVar/ExtVar/Value)[2]', ''Nvarchar(max)') AS MiddleInitial 
FROM dbo.Customer

which is great but what I'd really like to do is query the xml by 'Name' rather than the index ([1]) as these may be stored in different orders from time to time.

Basically what I need to know is how can I query by the value of 'Name' something like -

'(/ArrayOfExtVar/ExtVar/Value)[Rate Code]'

Could I add an attribute to the ExtVars Node and query on that instead?

Answer 1

It sounds like you want

/ArrayOfExtVar/ExtVar[Name = 'Rate Code']/Value

Answer 2

あなたはこのようなことをしようとしていますか？

DECLARE @input TABLE (ID INT, ExtVars XML)

INSERT INTO @input VALUES(1, '<ArrayOfExtVar xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <ExtVar>
    <Name xsi:type="xsd:string">Rate Code</Name>
    <Value xsi:type="xsd:string">E46</Value>
  </ExtVar>
  <ExtVar>
    <Name xsi:type="xsd:string">Middle Name</Name>
    <Value xsi:type="xsd:string">Henry</Value>
  </ExtVar>
</ArrayOfExtVar>')

SELECT
    Name = ExtVar.value('(Name)[1]', 'varchar(50)'),
    [Value] = ExtVar.value('(Value)[1]', 'varchar(50)')
FROM
    @input
CROSS APPLY
    ExtVars.nodes('/ArrayOfExtVar/ExtVar') AS XTbl(ExtVar)
WHERE   
    ID = 1

次のような出力を返します。

そしてもちろん、これに名前ベースのWHERE句を追加することもできます（結果を決定するためにXMLに「到達」します）。

SELECT
    Name = ExtVar.value('(Name)[1]', 'varchar(50)'),
    [Value] = ExtVar.value('(Value)[1]', 'varchar(50)')
FROM
    @input
CROSS APPLY
    ExtVars.nodes('/ArrayOfExtVar/ExtVar') AS XTbl(ExtVar)
WHERE   
    ExtVar.value('(Name)[1]', 'varchar(50)') LIKE 'Rate%'   -- or whatever you want

Answer 3

I don't know if SQL Server's implementation of XPath supports the parent (..) operator, but you could try this instead:

/ArrayOfExtVar/ExtVar/Name[text()='Rate Code']/../Value

This finds the Name node that has an inner text of 'Rate Code', then navigates to its parent and from there it goes to the Value node underneath it.

---

If you could add Name as an attribute of the ExtVar node, that would make it a bit easier:

Sample XML:

...
<ExtVar name="Rate Code">
    <Value xsi:type="xsd:string">E46</Value>
</ExtVar>
...

XPath:

/ArrayOfExtVar/ExtVar[@name='Rate Code']/Value

Answer 4

You can do axis steps in predicates, too.

//ExtVar[Name eq 'Rate Code']/Value