Just because a result is unexpected
does not mean its an incorrect result. No postgresql follows the order
of operations as expected.
Now looking at the 2 For loops the First does not have a where clause
and the Second has a Where not null this could be the cause of the
problem.
Another note you don't need to do this in nested For loops it can be
done in a single select statement using nested queries or by using a
join clause
Example of a Left Join
Select period, id,
(col2-avgResults.col2)/AvgResults.dev_col2,
(col1 - AvgResults.col1) / AvgResults.dev_col1
FROM scheme.table,
Left Join
(SELECT period, AVG(col1) AS avg_col1,
STDDEV(col1) AS
dev_col1, AVG(col2) AS avg_col2,
STDDEV(col2) AS dev_col2
FROM scheme.table
GROUP BY period
Where col1 is not null ) AvgResults
On AvgResults.period = scheme.table.period
WHERE col1
IS NOT NULL
Assuming i don't have any typos this should give you the results you are looking for and be faster.
You can throw in a Case statement in the select testing for grav to limit the result down and speed things up to a single column and do the update that why.
jc_mich wrote:
Hi all!
I'm developing an algorithm with PL/PGSQL using statistical operations from
a table. I have several differences between expected results and the results
generated by the function.
I want to know if there are differences in arithmetic operation sintax or if
there's any special arithmetical operators precedence between pl/pgsql and
other languages.
My code looks like this:
FOR iterator1 IN SELECT period, AVG(col1) AS avg_col1, STDDEV(col1) AS
dev_col1, AVG(col2) AS avg_col2, STDDEV(col2) AS dev_col2 FROM scheme.table
GROUP BY period ORDER BY period LOOP
FOR iterator2 IN SELECT period, id, col2, col1 FROM scheme.table WHERE col1
IS NOT NULL LOOP
IF grav = 0 THEN
_standata := (iterator2.col1 - iterator1.avg_col1) / iterator1.dev_col1;
ELSE
_standata := (iterator2.col2 - iterator1.avg_col2) / iterator1.dev_col2;
END IF;
UPDATE scheme.table SET standata = _standata WHERE id = iterator2.id AND
period=iterator2.period;
_standata := 0.0;
END LOOP;
END LOOP;
Thanks!
