Question

Is it possible to use an XML DML statement to rename an element in an untyped XML column?

I am in the process of updating an XML Schema Collection on an XML column and need to patch the existing XML instances by renaming one element before I can apply the latest schema.

As far as I can tell from the docs you can only insert / delete nodes or replace their value.

Answer 1

As the saying goes, “Where there’s a will there’s a way”

Here’s two methods:
the first is to simply replace the previous xml with a new xml constructed from the original with the new element name. In my example I’ve changed Legs/Leg to Limbs/Limb this could get very complicated for anything but the simplest schema

And secondly, a more appropriate approach of combining insert and delete.

I’ve combined them into one simple example:

declare @xml as xml = '<animal species="Mouse">
  <legs>
    <leg>Front Right</leg>
    <leg>Front Left</leg>
    <leg>Back Right</leg>
    <leg>Back Left</leg>
  </legs>
</animal>'

set @xml = (select 
     t.c.value('@species', 'varchar(max)') as '@species'
    ,(select
     ti.C.value('.', 'varchar(max)') 
from @Xml.nodes('//animal/legs/leg') ti(c) for xml path('limb'), /* root('limb'), */type) as    limbs   
from @xml.nodes('//*:animal') t(c) for xml path('animal'), type)

select @xml;

while (@xml.exist('/animal/limbs/limb') = 1) begin
    /*insert..*/
    set @xml.modify('
            insert <leg>{/animal/limbs/limb[1]/text()}</leg>
            before (/animal/limbs/limb)[1]
        ');
    /*delete..*/
    set @xml.modify('delete (/animal/limbs/limb)[1]');
end

set @xml.modify('
        insert <legs>{/animal/limbs/leg}</legs>
        before (/animal/limbs)[1]
    ');
set @xml.modify('delete (/animal/limbs)[1]');

select @xml;