T/SQL: Format results of SELECT on XML stored as nvarchar(max)

Question

I am not sure why, but our nLog configuration is now stored as an nvarchar(max) column in a table. With a standard SELECT on the column, I get output like:

<variable name="HeaderLayout".... 

I have tried using "FOR XML AUTO", as well as a series of REPLACE functions to get nice, pretty XML output from this column. Option A doesn't automatically cast the replacement markers to < or >, option B is really clumsy. Can someone please recommend a good why to retrieve the configuration as formatted XML?

As a bonus, I'd like to be able to take the formatted XML, make a change and then INSERT with a minimum of effort, but for now, I'd just settle for being able to make the SELECT results more readable.

Thank you!

Answer 1

First cast the value to XML. That will create an XML with your entire XML as a single value. Then you get that value from the XML using the value function and finally you cast the fetched value back to XML.

Here is some code using a table variable you can test on.

declare @T table
(
  Col nvarchar(max)
)

insert into @T(Col)
values('<root><item ID="1">textvalue</item></root>') 

select cast(cast(T.Col as xml).value('.', 'nvarchar(max)') as xml) as XMLCol
from @T as T

Result:

XMLCol
-------------------------------------------
<root><item ID="1">textvalue</item></root>

Answer 2

Try FOR XML AUTO, TYPE. And can you provide an example of your query?