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

> Date: Tue, 16 Nov 2010 17:23:16 +0100
> Subject: [GENERAL] Counting boolean values (how many true, how many false)
> From: alexander(dot)farber(at)gmail(dot)com
> To: pgsql-general(at)postgresql(dot)org
>
> Hello,
>
> if I have this table with 3 boolean columns:
>
> # \d pref_rate
> Table "public.pref_rep"
> Column | Type | Modifiers
> ------------+-----------------------------+---------------
> id | character varying(32) |
> author | character varying(32) |
> good | boolean |
> fair | boolean |
> nice | boolean |
> about | character varying(256) |
> last_rated | timestamp without time zone | default now()
> Foreign-key constraints:
> "pref_rate_author_fkey" FOREIGN KEY (author) REFERENCES pref_users(id)
> "pref_rate_id_fkey" FOREIGN KEY (id) REFERENCES pref_users(id)
>
> - how can I please count the number of
> true's and false's for each column for a certain id?
> (to find that persons rating)
>
> I'm trying:
>
> select sum(fair=true), sum(fair=false) from pref_rep;
>
> but sum() doesn't like a boolean as an argument.
>
> I've only come up with
>
> select count(*) from pref_rep where fair=true and id='XXX';
>
> but this would mean I have to call this line 6 times? (2 x column).

Hi,

You can use a 'sum()' with 'case when':

select
sum(case when fair then 1 else 0 end) as fair,
sum(case when good then 1 else 0 end) as good,
sum(case when nice then 1 else 0 end)
from public.pref_rep;