On Saturday, May 28, 2005, at 03:27 PM, Bruno Wolff III wrote:
On Sat, May 28, 2005 at 14:27:17 -0300,
David Pratt <fairwinds@xxxxxxxxxxx> wrote:
Pretty basic question. Is it necessary to add NOT NULL or UNIQUE NOT
NULL to SERIAL or is this implicit and unnecessary?
Serials no longer generate a uniqie index by default. So in practice
you will normally want to declare them as PRIMARY KEYs. However there
are cases where you don't need this and the index is extra overhead.
Alright. so would it be better form for me to to this in a
create_tables.sql
CREATE TABLE new_table (
id SERIAL,
description TEXT NOT NULL
);
And then in a create_primary_keys.sql do this for the tables requiring
it.
ALTER TABLE new_table ADD CONSTRAINT new_table_pkey PRIMARY KEY (id);
Does the PRIMARY KEY declaration ensure that the id values are unique?
Serial should always give me an incremented value that's different so I
am assuming it is unnecessary to use UNIQUE. Am I correct?
Regards,
David
