Re: I need help creating a query

On 15/07/2006, at 2:07 AM, Sergio Duran wrote:

> How about if we make it simpler, only 1 table
>
> 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?

Try this:

SELECT w2.*
FROM ( SELECT name,
MAX(startdate) AS startdate
FROM worker
GROUP BY name
)
AS w1
JOIN worker AS w2
ON (w1.name = w2.name
AND w1.startdate = w2.startdate);

Obviously you would use a real primary key instead of 'name' for the
join constraint but you get the idea

--
Seeya...Q

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