Sorry, I tried to make my subject as good as possible.

I have a table where I store the dates in which I take out of my inventory
(like "installation dates")

table
---------------
row_id SERIAL
date DATE
fk_item INTEGER

and that's pretty much it.

I want to have a query returning how long have been certain items lasting.

Say I have:

SELCT date FROM table WHERE fk_item = "INKJET_INK-BW"

date
-------------
2005-02-02
2005-03-05
2005-04-07
2005-05-02

I need something to calculate the intervals between those dates, like this:

intervals (in days)
--------------------
31
34
25

So I can get the stddev and stuff from the "duration" of the items.

I've been having a hard time with it. I'm trying NOT to program new
functions.

Any help will be appreciated.

--Octavio
--
Ing. Octavio Alvarez Piza, Jefe de Informática, TBC Universidad.
Tel.: +52 (664) 621-7111 ext. 133; E-mail: alvarezp(at)tecbc(dot)net