How to append to a text field in t-sql SQL Server 2005

in 2005 you should use varchar(max) or nvarchar(max) these columns will work with normal varchar functions. Text and ntext have been deprecated

Try this:

update 
  tablename
set
  fieldname = convert(nvarchar(max),fieldname) + 'appended string'

This should work (link)

Copied from link:

DECLARE @ptrval binary(16)
SELECT @ptrval = TEXTPTR(ntextThing)
FROM item
WHERE id =1
UPDATETEXT table.ntextthing @ptrval NULL 0 '!'
GO