How to update xml using value from a sql query

Question

I have a table with an XML column. I need to insert various nodes and then set those nodes using values from a sub-query.

Setup:

use tempdb

CREATE TABLE [dbo].[Sites](
    [SiteID] [int] IDENTITY(1,1) NOT NULL,
    [SiteInfo] [xml] NULL,
    [InVal] Varchar(50) NULL)

insert into [dbo].[Sites] ([InVal]) select 'ABC' union select 'DEF' union  select 'GHI'

update [dbo].[Sites] SET [SiteInfo] = '<SiteInfo />'

update [dbo].[Sites] SET [SiteInfo].modify('insert <SiteID/> into (/SiteInfo[1])') 

Here is my update in it's most simple form.

update Sites SET [SiteInfo].modify('replace value of (/SiteInfo/@SiteID)[1] with sql:column("InVal")') 

I have tried with both singleton and non singleton nodes

The end result should preferably not be a singleton. i.e something like:

<SiteInfo>
  <SiteID>ABC</SiteID>
</SiteInfo>

Answer 1

You've got nothing to replace in <SiteID/>. Try and use an insert instead:

update Sites SET [SiteInfo].modify('insert text{sql:column("InVal")} as first into (/SiteInfo/SiteID)[1]');