Message-ID: <3E4ACE74.109@openratings.com>
Date: Wed, 12 Feb 2003 17:45:08 -0500
From: Dmitry Tkach <dmitry@openratings.com>
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To: Nicholas Allen <nallen@freenet.co.uk>
Cc: Bruno Wolff III <bruno@wolff.to>, pgsql-sql@postgresql.org
Subject: Re: How do you select from a table until a condition is met?
References: <200302121910.38232.nallen@freenet.co.uk>
	<200302122055.21790.nallen@freenet.co.uk>
	<20030212203749.GA30483@wolff.to>
	<200302122153.08970.nallen@freenet.co.uk>
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Nicholas Allen wrote:

>Ok I thought of that but what happens if there is no primary key in the table? 
>
Then tough luck - as you said yourself, since everything else can be 
duplicated, the primary key is the only way to
tell for sure which exact row you are talking about.

>I can probably add primary keys to the table but I didn't design the tables 
>and so I have little (but luckily some) say over what columns appear in them. 
>What has actually happened is that we have a view on a table and the view 
>doesn't return the primary key.  I'll try and ask the database administrator 
>to add the primary keys.
>
>Thanks for the help though I guess it is the only way to do it. I was just 
>hoping there would be a way to do it without a promary key to prevent changes 
>to our database views.
>
I think you are better off redesigning your interface - even if you do 
modify the view, and use those suggestions I mentioned earlier,
it will be slow like hell, unless your table only contains a few hundred 
rows, in which case it doesn't matter if you send the whole table to the 
client every time,

Dima


>
>On Wednesday 12 Feb 2003 9:37 pm, Bruno Wolff III wrote:
>  
>
>>On Wed, Feb 12, 2003 at 20:55:21 +0100,
>>
>>  Nicholas Allen <nallen@freenet.co.uk> wrote:
>>    
>>
>>>I thought of this but the problem is that there may be multiple rows with
>>>the same value for the column I am sorting on. Eg if sorting on a surname
>>>then there may be 100s of people with the same surname so generating a
>>>where clause that selects up to the exact person previously selected is
>>>very difficult.
>>>      
>>>
>>Then you should sort on surname AND whatever you are using as the primary
>>key.
>>
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>g
>  
>