A few SQL questions

Hi all, I have a few slightly more advanced SQL questions (which is why I'm
here in the first place I suppose). I'm looking to migrate some applications
and databases from Sybase to Postgres, and I have a few portability-type
questions, or rather, questions on how to do the equivalent in Postgres.

1. In sybase, each column can have the same rule applied to it. You don't
have to create multiple rules for columns in different tables. For instance,
let's suppose that we require 5 digit numeric ids, using only a char(5)
type, but there's a constraint on that column that says it must adhere to
idrule, and idrule is defined as:

create rule idrule as @id like "[0-9][0-9][0-9][0-9][0-9]" (ugly, I know,
but i didn't write it)

Looking at the docs, it looks like postgres is quite different. I could
create a new type, I suppose, but is there any other way to do something
like this in postgres?

2. Is there any nice way to generate number sequences via select? In other
words, something along the lines of:
select 1 through 10 as number;
number
--------
1
2
3
4
5
6
7
8
9
10

but more syntactically correct and working.

Thanks much,
Peter Koczan