use tempdb;
set ansi_nulls, quoted_identifier, xact_abort on;
go

create procedure dbo.p1
as
begin
 declare @c int;
 select @c = count(*) from master.dbo.spt_values;

 create table #p1 (a int not null primary key clustered, b int);
 select @c = checksum_agg(checksum(*)) from #p1 where a = 10;
end;
go

create procedure dbo.p2
as
begin
 declare @c int;
 select @c = count(*) from master.dbo.spt_values;

 create table #p2 (a int not null, b int);
 alter table #p2 add primary key clustered (a);
 select @c = checksum_agg(checksum(*)) from #p2 where a = 10;
end;
go

exec dbo.p1;
exec dbo.p1;
go

exec dbo.p2;
exec dbo.p2;
go

drop procedure dbo.p1, dbo.p2;
go