Re: transposing data for a view

I think this might do the trick...

CREATE FUNCTION hori_view() RETURNS BOOLEAN AS '
DECLARE
view_select TEXT;
view_from TEXT;
view_where TEXT;
column_name TEXT;
last_column_name TEXT;
g_row generalized_table%ROWTYPE;
BEGIN
SELECT region INTO column_name
FROM generalized_table ORDER BY region LIMIT 1;
view_select := ''SELECT '' || column_name ||
''.scanid, '' || column_name || ''.volume AS "'' ||
column_name || ''_volume"'';
view_from := '' FROM generalized_table '' || column_name;
view_where := '' WHERE '' ||column_name ||
''.region = '''''' || column_name || '''''''';
last_column_name := column_name;
FOR g_row IN SELECT DISTINCT ON (region) *
FROM generalized_table ORDER BY region OFFSET 1 LOOP
view_select := view_select || '', '' || g_row.region ||
''.volume AS "'' || g_row.region || ''_volume"'';
view_from := view_from || '' JOIN generalized_table '' ||
g_row.region || '' ON ('' || last_column_name ||
''.scanid = '' || g_row.region || ''.scanid)'';
view_where := view_where || '' AND '' || g_row.region ||
''.region = '''''' || g_row.region || '''''''';
last_column_name := g_row.region;
END LOOP;
EXECUTE ''CREATE VIEW generalized_view AS '' || view_select ||
view_from || view_where;
RETURN TRUE;
END;
' LANGUAGE 'plpgsql';

SELECT hori_view();

SELECT * FROM generalized_view;

Ok, it may not be pretty but it works,

Regards,

Aasmund.

On Wed, 31 Oct 2001 12:42:10 -0800, "Josh Berkus" <josh(at)agliodbs(dot)com> wrote:
> Jeremy,
>
> First, to do a pivot table, you have to be using Postgres 7.1.x. 7.0.x
> will not do it. So upgrade now.
>
>
> There are two approaches, the simple approach and the complex. The
> simple approach requires you to know in advance of building the view all
> of the possible values for your category column. The complex approach,
> which is dynamic, requires a rather sophisticated function (which I will
> write eventually, really!) so we won't go into it here.
>
> The simple approach is to create each column as a sub-select in the FROM
> clause of your statement. So, per the example above:
>
> SELECT scanid, A_volume, B_volume, C_volume
> FROM (SELECT scanid FROM volumes GROUP BY scanid) scan
> LEFT OUTER JOIN
> (SELECT scanid, volume as A_volume FROM volumes WHERE region = 'A') av
> ON scan.scanid = av.scanid LEFT OUTER JOIN
> (SELECT scanid, volume as B_volume FROM volumes WHERE region = 'B') bv
> ON scan.scanid = bv.scanid LEFT OUTER JOIN
> (SELECT scanid, volume as C_volume FROM volumes WHERE region = 'C') cv
> ON scan.scanid = cv.scanid
> ORDER BY scanid;
>
> This approach can be adapted to include aggregates and the like.
>
> -Josh Berkus
>
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> Josh Berkus
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Aasmund Midttun Godal

aasmund(at)godal(dot)com - http://www.godal.com/
+47 40 45 20 46