Do you like this
create table #pc (idno int,p varchar(8))
insert into #pc values (0,'AA1 BB1')
insert into #pc values (0,'AA1 BB1')
insert into #pc values (0,'AA1 BB1')
insert into #pc values (0,'AA2 BB2')
insert into #pc values (0,'AA2 BB2')
insert into #pc values (0,'AA2 BB2')
insert into #pc values (0,'AA2 BB2')
insert into #pc values (0,'AA2 BB2')
insert into #pc values (0,'AA3 BB3')
declare @idno int,@p varchar(8)
set @idno=0
set @p=''
update #pc set @idno=(case when p<>@p then 1 else @idno+1 end),idno=@idno,@p=p
select * from #pc
idno p
----------- --------
1 AA1 BB1
2 AA1 BB1
3 AA1 BB1
1 AA2 BB2
2 AA2 BB2
3 AA2 BB2
4 AA2 BB2
5 AA2 BB2
1 AA3 BB3
Far away is close at hand in the images of elsewhere.
Anon.