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Date: Sat, 14 Jan 2006 08:13:33 -0500
From: "D'Arcy J.M. Cain" <darcy@druid.net>
To: Alan Chandler <alan@chandlerfamily.org.uk>
Cc: pgsql-sql@postgresql.org
Subject: Re: Another orderby problem
Message-Id: <20060114081333.3d1f223b.darcy@druid.net>
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References: <200601141302.49630.alan@chandlerfamily.org.uk>
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On Sat, 14 Jan 2006 13:02:48 +0000
Alan Chandler <alan@chandlerfamily.org.uk> wrote:
> select name, id, transaction.date as tdate, description, -amount as amount
> from account left join transaction on name=src where name = 'Sarah' 
> union
> select name, id, transaction.date as tdate, description, amount
> from account join transaction on name=dst where name ='Sarah'
> order by tdate asc;
> 
>  name  | id |   tdate    |        description        | amount
> -------+----+------------+---------------------------+--------
>  Sarah | 12 | 0005-06-05 | Ben 21st Birthday Pressie |     41
>  Sarah | 13 | 0005-06-05 | Cash from Mum             |     60
>  Sarah | 14 | 0005-06-08 | Petrol                    |  27.33
>  Sarah | 15 | 0005-06-10 | Petrol Allowance          |    -40
>  Sarah | 11 | 2005-06-05 | Sarah Petrol              |  27.74
> (5 rows)
> 
> I can't figure out why the dates are not in order (see transaction 11 is out 
> of place).  

It looks to be in order to me.  Transaction 11 is 2,000 years later
than the others.  I suppose you are letting people enter two digit
dates without running it through a cleaner process.  If you put "05" as
a year into a date field, PostgreSQL will take you at your word.

if year < 50:
  year += 2000
elif year < 100:
  year += 1900

That will probably handle most cases for you.  Alternatively, don't
allow dates outside of your known domain.

-- 
D'Arcy J.M. Cain <darcy@druid.net>         |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 425 1212     (DoD#0082)    (eNTP)   |  what's for dinner.