My guess is that it is Object Explorer in SSMS that generates this query. Should be easy to verify with a trace and clicking around a bit in OE.
Add column on table cause blocking
I was adding column on one of my user table and found out that my alter table query blocked another query which i have no idea where does it come from .
ALTER TABLE [dbo].[table] ADD [column] [int] NOT NULL DEFAULT 0
and this is the query which has been blocked by my add column spid as below
and this is the wait resource key
This is object ID for index 281474978938880
I believe a system query blocked by my add column query. Does anyone have idea what is that system query and why it is blocked when i m adding column on database which currently used by me only.