Re: Counting boolean values (how many true, how many false)

On 16 November 2010 17:02, Thom Brown <thom@linux.com> wrote:
> On 16 November 2010 16:49, maarten <maarten.foque@edchq.com> wrote:
>> Hi,
>>
>> sum doesn't like booleans, but it does like integers so:
>> sum(boolval::int) solves that problem for you.
>>
>> SELECT id,sum(good::int + fair::int + nice::int) would get you a total
>> of the three for each row
>>
>> good luck,
>> Maarten
>
> Or, if you want a more flexible solution, you could try this:
>
> CREATE OR REPLACE FUNCTION countif_add(current_count int, expression bool)
> RETURNS int AS
> $BODY$
> BEGIN
>        IF expression = true THEN
>                RETURN current_count + 1;
>        ELSE
>                RETURN current_count;
>        END IF;
> END;
> $BODY$
> LANGUAGE plpgsql
>
> CREATE AGGREGATE countif (boolean)
> (
>    sfunc = countif_add,
>    stype = int,
>    initcond = 0
> );
>
> Then you can call:
>
> SELECT countif(fair) AS 'total fair', countif(!fair)
> AS 'total unfair'
> FROM pref_rep;

Correction here... you can't use !boolean... it would need to be...

SELECT countif(fair) AS 'total fair', countif(not fair) AS 'total unfair'

--
Thom Brown
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