From: Christoph Haller <ch@rodos.fzk.de>
Message-Id: <200207110837.KAA07881@rodos>
Subject: Re: SQL problem with aggregate functions.
To: david.bouriaud@ac-rouen.fr (David BOURIAUD)
Date: Thu, 11 Jul 2002 10:37:40 METDST
Cc: pgsql-sql@postgresql.org
In-Reply-To: <200207091036.17913.david.bouriaud@ac-rouen.fr>;
	from "David BOURIAUD" at Jul 9, 102 2:50 pm

> 
> I've got a table in which there is a field that can have one amongst 3 
> possible values : D, R, X. Is it possible to get in one query the count of 
> this different values.Please, note that I don't want to have a querry like 
> this :
> "select count (*) from tab group by f1;", cause i want to get all the possible 
> count values in one row (these data are already grouped on another field).
> To give a more accurate example, here is what I want to retrieve :
> 
> Field group | count of D | count of R | count of X.
> 
> Any clues ?
> -- 
What about something like 


SELECT SUM(f1_d) AS count_d,
       SUM(f1_r) AS count_r,
       SUM(f1_x) AS count_x
FROM (
 SELECT CASE WHEN f1 = 'D' THEN 1 ELSE 0 END AS f1_d,
        CASE WHEN f1 = 'R' THEN 1 ELSE 0 END AS f1_r,
        CASE WHEN f1 = 'X' THEN 1 ELSE 0 END AS f1_x
 FROM tab ) AS foo ;

Regards, Christoph