Hi,
I have a problem with a query wich simple aggregate values. In the sample
below I have two values, 1.3 and 1.4. Rounding their average with one
decimals, should give 1.4.
The first query with - cast( tables_seb.tbl_arvier_chamencon.id_1 AS
numeric) AS value - give the expected result, while the second one with -
tables_seb.tbl_arvier_chamencon.id_1 AS value - give 1.3.
Which could be the reason ??
-- data
fulldate timestamp; tables_seb.tbl_arvier_chamencon.id_1- reals
2009-03-29 00:00:00; 1.3
2009-03-29 00:30:00; 1.4
--Good query
SELECT date_trunc('hour', data) AS data, round(cast(avg(value) AS numeric),
1 ) AS value
FROM
(
SELECT _master_30.fulldate AS data,
cast( tables_seb.tbl_arvier_chamencon.id_1 AS numeric) AS
value
--tables_seb.tbl_arvier_chamencon.id_1 AS value
FROM _master_30
LEFT JOIN tables_seb.tbl_arvier_chamencon ON
_master_30.fulldate = tables_seb.tbl_arvier_chamencon.fulldate
WHERE _master_30.fulldate between '2009-03-29 00:00:00' AND
'2009-03-29 00:59:59'
ORDER BY data
) foo
GROUP BY 1 ORDER BY 1;
-- value = 1.4 OK
--wrong query
SELECT date_trunc('hour', data) AS data, round(cast(avg(value) AS numeric),
1 ) AS value
FROM
(
SELECT _master_30.fulldate AS data,
--cast( tables_seb.tbl_arvier_chamencon.id_1 AS numeric) AS
value
tables_seb.tbl_arvier_chamencon.id_1 AS value
FROM _master_30
LEFT JOIN tables_seb.tbl_arvier_chamencon ON
_master_30.fulldate = tables_seb.tbl_arvier_chamencon.fulldate
WHERE _master_30.fulldate between '2009-03-29 00:00:00' AND
'2009-03-29 00:59:59'
ORDER BY data
) foo
GROUP BY 1 ORDER BY 1
-- value = 1.3 NOT OK
-- test
select round(cast( (1.3 + 1.4)::real / 2 as numeric), 1);
-- value = 1.4 OK
Using PostgreSQL 8.3.7 on Windows Server 2008
Thank in advance,
Paolo Saudin
