Re: Setting boolean column based on cumulative integer value

am Sat, dem 02.12.2006, um 0:50:37 +1100 mailte Markus Juenemann folgendes:
> I've got a bit of a tricky (for me!) problem. The example below is
> completely ficticious but
> describes my real problem in a way which might be easier to understand.
>
> Imagine the table contains a list of passenger wanting to get on a
> small(!) plane.
> The plane can carry at most 200kg of passengers and will be filled
> strictly on a first-come
> first-serve basis - well, check-in staff is a bit stupid ;-). So what
> needs to be done is to set the 'gets_seat' column to true until the
> weight limit is reached.

With your example, i wrote a little function for this:

---%<------
create or replace function check_wight( out id int,
out name text,
out weight int,
out gets_seat boolean ) returns setof record as $$
declare rec record;
sum int;
begin
sum = 0;
for rec in select * from passenger_queue order by id LOOP
id = rec.id;
name = rec.name;
weight = rec.weight;
sum = sum + weight;
if sum < 200 then
gets_seat='t'::bool;
else
gets_seat='f'::bool;
end if;
return next ;
end loop;
end
$$ language plpgsql;
---%<------

test=# select * from passenger_queue;
id | name | weight | gets_seat
----+-------+--------+-----------
1 | Peter | 75 | f
2 | Mary | 50 | f
3 | John | 70 | f
4 | Steve | 80 | f
(4 rows)

test=# select * from check_wight();
id | name | weight | gets_seat
----+-------+--------+-----------
1 | Peter | 75 | t
2 | Mary | 50 | t
3 | John | 70 | t
4 | Steve | 80 | f
(4 rows)

HTH, Andreas
--
Andreas Kretschmer
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