Message-ID: <46ADC217.7010607@archonet.com>
Date: Mon, 30 Jul 2007 11:48:55 +0100
From: Richard Huxton <dev@archonet.com>
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To: Jay Kang <arrival123@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Questions on Tags table schema
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	<d251ee4a0707300313y5e648fa3kdc5df88180df82db@mail.gmail.com>
	<46ADBD35.4000304@archonet.com>
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Richard Huxton wrote:
> 
>> CREATE TABLE car_tags
>> (
>>    CarID integer NOT NULL,
>>    TagID integer NOT NULL
>> );
> [snip other table defs]
> 
> Don't forget CarID isn't really an integer (I mean, you're not going to 
> be doing sums with car id's are you?) it's actually just a unique code. 
> Of course, computers are particularly fast at dealing with 32-bit integers.

Just realised I haven't explained what I meant by that.

CarID is a different type from PlaneID and TagID. As it happens, we are 
using integers to represent them all, but a CarID = 1 is different from 
a PlaneID = 1 and although you can numerically compare the two it is an 
error to do so.

-- 
   Richard Huxton
   Archonet Ltd