Re: can i make this sql query more efficiant?

On 03 Apr 2003 16:02:04 -0500, Robert Treat
<xzilla@users.sourceforge.net> wrote:
>select 
>    event, 
>    (select count(*) from baz a 
>        where level = 1 and a.event=baz.event) as ones, 
>    (select count(*) from baz a 
>        where level = 2 and a.event=baz.event) as twos, 
>    (select count(*) from baz a 
>        where level = 3 and a.event=baz.event) as threes
>from
>     baz
>group by 
>    event;

>which is fine, but I am wondering if there is a better way to do this?
>I'd mainly like to reduce the number of subqueries involved.

SELECT event,      SUM (CASE level WHEN 1 THEN 1 ELSE 0 END) AS ones,      SUM (CASE level WHEN 2 THEN 1 ELSE 0 END) AS
twos,     SUM (CASE level WHEN 3 THEN 1 ELSE 0 END) AS threes FROM bazGROUP BY event;
 

> Another
>improvement would be to not have to explicitly query for each level,

This might be a case for a clever set returning function, but that's
not my realm.  Wait for Joe to jump in  ;-)

ServusManfred