Re: Equivalent for AUTOINCREMENT?

On Sat, Nov 01, 2008 at 02:24:37PM +0100, Michelle Konzack wrote:
> Du I need to create a SEQUENCE for each table or do I need only ONE of
> if and can use it independant on differnt tables?

If you just create a bunch of tables with SERIAL or BIGSERIAL columns,
it will create one sequence for each column. But you can make a set of
such columns use the same sequence if you want. SERIAL and BIGSERIAL are
really just "syntactic sugar" which create a sequence and set the
column's default value to the next value in the sequence, like this:

jtolley=# create table a (id serial);
NOTICE: CREATE TABLE will create implicit sequence "a_id_seq" for
serial column "a.id"
CREATE TABLE
jtolley=# \d a
Table "public.a"
Column | Type | Modifiers
--------+---------+------------------------------------------------
id | integer | not null default nextval('a_id_seq'::regclass)

If I need a new table or column using the same sequence, I just do this:

jtolley=# create table b (q integer not null default
nextval('a_id_seq'));
CREATE TABLE
jtolley=# \d b
Table "public.b"
Column | Type | Modifiers
--------+---------+------------------------------------------------
q | integer | not null default nextval('a_id_seq'::regclass)

- Josh / eggyknap