On Fri, 11 May 2007 14:47:04 +1000, Andrew Shea <[EMAIL PROTECTED]> wrote:
> The following works as expected:
>
> select (SELECT CASE WHEN (1=2) THEN 0 ELSE sum(count) END) from (
> select 1 as count union select 2 union select 3
> ) as "temp";
>
> The result is "6".
>
> The following also works as expected:
>
> select count(*) from (
> select 1 as count union select 2 union select 3
> ) as "temp";
>
> The results is "3".
>
>
> However the following code doesn't work even though it is very similar
> to the first query (that is, and aggregate function within a case
> statement):
>
> select (SELECT CASE WHEN (1=2) THEN 0 ELSE COUNT(*) END) from (
> select 1 as count union select 2 union select 3
> ) as "temp";
>
> The result is three rows of "1".
>
> So why does the "count" aggregate function within a case statement
> execute on a per row basis whereas the "sum" aggregate within a case
> statement will first group the rows?
The * from count(*) binds to the inner most select where it can draw
data.
Think of it like
select
(select count('1') from bar)
>from foo
foo and bar have nothing to do with each other so it turns into for each
row in foo count the number of records in bar.
klint.
+---------------------------------------+-----------------+
: Klint Gore : "Non rhyming :
: EMail : [EMAIL PROTECTED] : slang - the :
: Snail : A.B.R.I. : possibilities :
: Mail University of New England : are useless" :
: Armidale NSW 2351 Australia : L.J.J. :
: Fax : +61 2 6772 5376 : :
+---------------------------------------+-----------------+
---------------------------(end of broadcast)---------------------------
TIP 4: Have you searched our list archives?
http://archives.postgresql.org
