Re: Determine the time difference from records in a select - Mailing list pgsql-sql

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

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