Message-ID: <3D13666B.AC687A4A@nsd.ca>
Date: Fri, 21 Jun 2002 13:46:19 -0400
From: Jean-Luc Lachance <jllachan@nsd.ca>
MIME-Version: 1.0
To: josh@agliodbs.com
Cc: pgsql-sql@postgresql.org
Subject: Re: SQL Challenge:  Skip Weekends
References: <200206201713.03801.josh@agliodbs.com>
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here is the algorithm:

date := now - day_of_the_week
interval := interval + day_of_the_week
date := date + int( interval/5)x7 + ( interval mod 5)


Josh Berkus wrote:
> 
> Folks,
> 
> Hey, I need to write a date calculation function that calculates the date
> after a number of *workdays* from a specific date.   I pretty much have the
> "skip holidays" part nailed down, but I don't have a really good way to skip
> all weekends in the caluclation.  Here's the ideas I've come up with:
> 
> Idea #1: Use a reference table
> 1. Using a script, generate a table of all weekends from 2000 to 2050.
> 2. Increase the interval by the number of weekends that fall in the relevant
> period.
> 
> Idea #2:  Some sort of calculation using 5/7 of the interval, adjusted
> according to the day of the week of our starting date.  My head hurts trying
> to figure this one out.
> 
> --
> -Josh Berkus
> 
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