Re: How to select by proximity

Can OFFSET be a negative number?
What I was looking for is a way to access the +1 and -1 record with SQL as seen on the screen when you do a select using an index or a sort.
With PgAdmin when you  see a record of interest in the middle of the display, you can visually see the one above and below.
I seem to remember that in Informix I had a go + or -  inside a pointer loop.
 

________________________________
From: Postgres <DStaal(at)usa(dot)net>
To: pgsql-novice(at)postgresql(dot)org
Sent: Monday, May 14, 2012 5:24 PM
Subject: Re: [NOVICE] How to select by proximity

On 2012-05-14 14:00, Francisco Leovey wrote:
> Hello group
>
> I have a large table indexed by a varchar column
> I would like to select records that are around the hit value, say
> "Marriot" by index order
> How can I retrieve the prior and next in order?
> Is there a goto "Marriot" and then a goto +1 and goto -1 SQL facility?

The LIMIT and OFFSET commands in a SELECT statement (in combination with ORDER BY) should be helpful here.

However, it's important to remember the the database has no real concept of 'index order': All data is unordered unless ask it to be ordered.  It's not going through a list until it gets to 'Marriot', and then returning that to you; it's returning a set which includes 'Marriot'.  To do what you want, you'll likely need to return the *entire* table, and then pull out what parts you want.  The LIMIT and OFFSET would only be helpful once you know where 'Marriot' appears in the (ordered) result of your particular query at a particular point in time.

Daniel T. Staal

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