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?

On 2012-05-14 14:00, Francisco Leovey wrote:
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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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:
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 onlybe helpful once you know where 'Marriot' appears in the (ordered) result of your particular query at a particular point in time.

Daniel T. Staal

---------------------------------------------------------------
This email copyright the author.* Unless otherwise noted, you
are expressly allowed to retransmit, quote, or otherwise use
the contents for non-commercial purposes.* This copyright will
expire 5 years after the author's death, or in 30 years,
whichever is longer, unless such a period is in excess of
local copyright law.
---------------------------------------------------------------

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On 05/15/2012 04:30 AM, Francisco Leovey wrote:
surrounding records like this:

with prev as (select * from yourtable where yourcolumn <= 'Marriot'
order by yourcolumn desc limit 6),
next as (select * from yourtable where yourcolumn > 'Marriot' order
by yourcolumn limit 5),
select * from prev
union
select * from next
order by yourcolumn
;

But if "yourcolumn" is not unique, your results may be unpredictable.

Cheers,
Steve

That works fine, thank you!



________________________________
From: Steve Crawford <scrawford (AT) pinpointresearch (DOT) com>
To: Francisco Leovey <fleovey (AT) yahoo (DOT) com>
Cc: "pgsql-novice (AT) postgresql (DOT) org" <pgsql-novice (AT) postgresql (DOT) org>
Sent: Tuesday, May 15, 2012 12:49 PM
Subject: Re: [NOVICE] How to select by proximity



On 05/15/2012 04:30 AM, Francisco Leovey wrote:
Can OFFSET be a negative number?

with prev as (select * from yourtable where yourcolumn <=
'Marriot' order by yourcolumn desc limit 6),
*** next as (select * from yourtable where yourcolumn > 'Marriot'
order by yourcolumn limit 5),
select * from prev
union
select * from next
order byyourcolumn
;

But if "yourcolumn" is not unique, your results may be
unpredictable.

Cheers,
Steve