create table worker(
name varchar(50),
position varchar(50),
startdate date,
salary numeric(9,2));
insert into worker values ('Jon', 'boss', '2001-01-1', 1000.00);
insert into worker values ('Peter', 'cleaning', '2002-01-01', 100.00);
insert into worker values ('Peter', 'programming', '2004-01-01', 300.00);
insert into worker values ('Peter', 'management', '2006-01-01', 500.00);
select * from worker;
name | position | startdate | salary
-------+-------------+------------+---------
Jon | boss | 2001-01-01 | 1000.00
Peter | cleaning | 2002-01-01 | 100.00
Peter | programming | 2004-01-01 | 300.00
Peter | management | 2006-01-01 | 500.00
I want to group by name, order by date desc and show the first grouped salary, maybe I should write an aggregate function that saves the first value and ignores the next ones. Is there already an aggregate function that does this? I havent written any aggregate functions yet, can anybody spare some pointers?
On 7/14/06, Sergio Duran <sergioduran@xxxxxxxxx> wrote:
Nice, Richard, but you use max(startdate), how about the salary? i cant use max(salary) how about if he got a pay cut?
My current solution is to write the nested query on the field list, like
SELECT worker.*,
(select salary
FROM position where worker_id=worker.worker_id
and fecha<='2006-04-01' LIMIT 1) as salary
FROM worker;
but I can only return 1 column from that subquery and repeating the same subquery for each column needed (position, date and salary) seems a little too much, if I write a procedure would postgres would optimize the access?On 7/13/06, Richard Broersma Jr < rabroersma@xxxxxxxxx> wrote:>
> worker: worker_id, name
> position: position_id, worker_id, position, startdate, salary
>
> If I perfom a query joining both tables, I can obtain all the workers and
> the positions the've had.
>
> SELECT name, startdate, position, salary FROM worker JOIN position
> USING(worker_id);
> worker1 | 2001-01-01 | boss | 999999
> worker2 | 2001-01-01 | cleaning | 100
> worker2 | 2006-04-01 | programmer | 20000
> worker2 | 2006-07-04 | management | 25000
>
> so far so good, now I need to obtain all the workers only with the position
> they had on a given date.
> if I wanted to know the positions on '2006-05-01' it would return
> worker1 | 2001-01-01 | boss | 999999
> worker2 | 2006-04-01 | programmer | 20000
>
This is just a quick guess. I am not sure if the logic is correct but it could be a starting
point.
select P2.worker_id, P2.pdate, P1.position, P1.salary
from position as P1
join
(select worker_id, max(startdate) as pdate
from position
where startdate <= '2006-05-01'
group by worker_id, position_id) as P2
on (P1.worker_id = P2.worker_id) and (P1.startdate = P2.pdate)
;
Regards,
Richard Broersma Jr.
