Обсуждение: Determine the time difference from records in a select

I apologize in advance, 'cause I think this was addressed a couple of months
ago, but I cannot find it in the archives.

I have a firewall hit database which keeps the date of the hit and the
offenders IP (among other items).  I would like to be able to execute a
select which would show each unique IP and the time difference from the
latest hit to the first hit.  I can do this in scripts, but was wondering if
there is a pure SQL query/queries way to accomplish this.

Help?
Rob

Robert Creager
Senior Software Engineer
Client Server Library
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Robert,

> I have a firewall hit database which keeps the date of the hit and
> the
> offenders IP (among other items).  I would like to be able to execute
> a
> select which would show each unique IP and the time difference from
> the
> latest hit to the first hit.  I can do this in scripts, but was
> wondering if
> there is a pure SQL query/queries way to accomplish this.

You need to use a subselect in the FROM clause, which requires 7.1 or
greater.

SELECT agg_last.ip_addr, first_hit, last_hit, (last_hit- first_hit) AS
hit_interval
FROM     (SELECT ip_addr, max(hit_date) FROM hits GROUP BY ip_addr)
agg_last,    (SELECT ip_addr, min(hit_date) FROM hits GROUP BY ip_addr)
agg_first
WHERE agg_last.ip_addr = agg_first.ip_addr;

-Josh Berkus

______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco
 

Robert:

> I have a firewall hit database which keeps the date of the hit and
> the
> offenders IP (among other items).  I would like to be able to execute
> a
> select which would show each unique IP and the time difference from
> the
> latest hit to the first hit.  I can do this in scripts, but was
> wondering if
> there is a pure SQL query/queries way to accomplish this.

You need to use a subselect, which means you need to be running 7.1 or
better.  Here's the basic idea:

SELECT agg_last.ip_address, first_hit, last_hit, (last_hit - first_hit)
AS hit_interval FROM
(SELECT ip_address, min(hit_date) as first_hit 



______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco