Re: query based on row number for psql8.3 - Mailing list pgsql-sql

From Michael Moore
Subject Re: query based on row number for psql8.3
Date
Msg-id CACpWLjOH5EUdHXozQNop_nnNdQf1kx39kziz1is42mUVEQyuNA@mail.gmail.com
Whole thread Raw
In response to Re: query based on row number for psql8.3  (Stephen Tahmosh <stahmosh@shieldsrx.com>)
List pgsql-sql
It was hinted at in previous responses, but if you do:

Select * from t1;
       and then again
select * from t1;

You have no guarantee that the results will be in the same order. So, even if your query DID work, it would be meaningless because you should consider the records to come in a random order.  Never assume the order, always specify it if it is important. 
Mike

On Wed, Mar 23, 2016 at 11:57 AM, Stephen Tahmosh <stahmosh@shieldsrx.com> wrote:


-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Rob Sargent
Sent: Wednesday, March 23, 2016 2:27 PM
To: pgsql-sql@postgresql.org
Subject: Re: [SQL] query based on row number for psql8.3



On 03/23/2016 12:00 PM, Emi wrote:
> Hello,
>
> For psql8.3, is there a simple way to query based on row number please?
>
> For example,
>
> select  case
>                     when row_num=1 THEN    t1.tot_hr
>                     ELSE t1.tot_hr - t1.pre_hr
>           END
> FROM  t1 ;
>
>
>
>
>
I seem to recall other posts from condordia:  Someone needs to take of
their skates and update postgres!

[ST]
I'm not  sure if this link works, as I don't have access to 8.3
http://postgresql.nabble.com/How-to-realize-ROW-NUMBER-in-8-3-td4328448.html

If this works, then wrap the query with a main query that uses "rownum" in the case statement.

STeve



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