From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
---|---|
To: | Leif Biberg Kristensen <leif(at)solumslekt(dot)org> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: DDL problems: Referential issue? |
Date: | 2009-11-04 20:25:53 |
Message-ID: | dcc563d10911041225j3d09c78fp2410ed99c7ba886e@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
On Wed, Nov 4, 2009 at 1:14 PM, Leif Biberg Kristensen
<leif(at)solumslekt(dot)org> wrote:
> On Wednesday 4. November 2009 21.03.26 Scott Marlowe wrote:
>> On Wed, Nov 4, 2009 at 11:53 AM, Leif Biberg Kristensen
>> > This looks strange to me, but it works:
>> >
>> > pgslekt=> CREATE TABLE participant_notes (
>> > pgslekt(> person_fk INTEGER NOT NULL,
>> > pgslekt(> event_fk INTEGER NOT NULL,
>> > pgslekt(> part_note TEXT,
>> > pgslekt(> PRIMARY KEY (person_fk, event_fk),
>> > pgslekt(> FOREIGN KEY (person_fk, event_fk) REFERENCES participants
>> > (person_fk, event_fk)
>> > pgslekt(> );
>> > NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
>> > "participant_notes_pkey" for table "participant_notes"
>> > CREATE TABLE
>>
>> Note that this will limit you to one record in your participant notes
>> for each record in the participants table.
>
> That's exactly what I want :)
>
> For all practical purposes, the design is equivalent to adding a TEXT column
> to the participants table. But as I expect a very small number of notes
> compared to the number of rows in the participants table, I prefer to create a
> small extra table rather than having a large number of null values in the
> participants table. Performance-wise, it probably doesn't matter much. It's
> more a matter of taste.
Exactly. Note that null values i pgsql take up VERY little space, so
performance-wise one table is likely faster, but it's not gonna break
the bank to have two.
From | Date | Subject | |
---|---|---|---|
Next Message | Bryce Nesbitt | 2009-11-04 21:00:32 | Mangled high bit characters with pg_server_prepare=0 in DBD::Pg |
Previous Message | Leif Biberg Kristensen | 2009-11-04 20:14:32 | Re: DDL problems: Referential issue? |