To: Terry Brick <terry_brick2000@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Formatting Functions and Group By 
In-reply-to: <20040413161305.22857.qmail@web11502.mail.yahoo.com> 
References: <20040413161305.22857.qmail@web11502.mail.yahoo.com>
Comments: In-reply-to Terry Brick <terry_brick2000@yahoo.com>
	message dated "Tue, 13 Apr 2004 09:13:05 -0700"
Date: Tue, 13 Apr 2004 13:33:18 -0400
Message-ID: <24390.1081877598@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Terry Brick <terry_brick2000@yahoo.com> writes:
> I'm porting a bunch of queries from MySQL to Postgres 7.4 and am having a problem with one
> particular area.  For example, a query like this works in MySQL:

> select
>   to_char(myCol,'Mon YY')
> from
>   myTable
> group by
>   to_char(myCol,'MM YYYY')
> order by
>   to_char(myCol,'MM YYYY')

Ah, good ol' MySQL :-( ... let the user do what he wants whether the
result is well defined or not ...

I'd suggest doing the grouping/ordering numerically rather than
textually.  For instance,

select
  to_char(date_trunc('month', myCol), 'Mon YY')
from
  myTable
group by
  date_trunc('month', myCol)
order by
  date_trunc('month', myCol);

Now this assumes you really want a time-based ordering, which the quoted
example doesn't give --- you've got month sorting to the left of year,
is that really what you want?  If it is then you'd need to go

group by
  date_trunc('month', myCol)
order by
  to_char(date_trunc('month', myCol), 'MM YYYY')

			regards, tom lane