On 2/21/07, Dan Harris [EMAIL PROTECTED] wrote:
I have a new task of automating the export of a very complex Crystal
Report. One thing I have learned in the last 36 hours is that the
export process to PDF is really, really, slooww..
Anyway, that is none of your concern. But, I am thinking that I can
somehow utilize some of PG's strengths to work around the bottleneck in
Crystal. The main problem seems to be that tens of thousands of rows of
data must be summarized in the report and calculations made. Based on
my recent experience, I'd say that this task would be better suited to
PG than relying on Crystal Reports to do the summarizing.
The difficulty I'm having is that the data needed is from about 50
different snapshots of counts over time. The queries are very simple,
however I believe I am going to need to combine all of these queries
into a single function that runs all 50 and then returns just the
count(*) of each as a separate column in a single row.
I have been Googling for hours and reading about PL/pgsql functions in
the PG docs and I have yet to find examples that returns multiple items
in a single row. I have seen cases that return sets of, but that
appears to be returning multiple rows, not columns. Maybe this I'm
barking up the wrong tree?
Here's the gist of what I need to do:
1) query count of rows that occurred between 14 months ago and 12 months
ago for a given criteria, then count the rows that occurred between 2
months ago and current. Repeat for 50 different where clauses.
2) return each count(*) as a column so that in the end I can say:
select count_everything( ending_date );
and have it return to me:
count_a_lastyear count_a_last60count_b_lastyearcount_b_last60
----
100150 200 250
I'm not even sure if a function is what I'm after, maybe this can be
done in a view? I am embarrassed to ask something that seems like it
should be easy, but some key piece of knowledge is escaping me on this.
this could be be done in a view, a function, or a view function combo.
you can select multiple counts at once like this:
select (select count(*) from foo) as foo, (select count(*) from bar) as bar;
but this may not be appropriate in some cases where something complex
is going on. you may certainly return multiple columns from a single
call using one of two methods:
* out parameters (8.1+)
* custom type
both of which basically return a record instead of a scalar. any
function call can be wrapped in a view which can be as simple as
create view foo as select * from my_count_proc();
this is especially advised if you want to float input parameters over
a table and also filter the inputs via 'where'.
merlin
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