Re: first_value/last_value

It would really save all the troubles for many people if postgresql has a
built-in first/last function along with sum/avg.
There is already a C extension and a wiki sample and implemented for
window function.
I am curious why these two functions were not added along their window
implementation counter part,
for completness and consistency

On Wed, May 18, 2016 at 10:42 PM, Melvin Davidson <melvin6925(at)gmail(dot)com>
wrote:

>
>
> On Wed, May 18, 2016 at 10:36 PM, Adam Brusselback <
> adambrusselback(at)gmail(dot)com> wrote:
>
>> Here is an example that works in a single query. Since you have two
>> different orders you want the data back in, you need to use subqueries to
>> get the proper data back, but it works, and is very fast.
>>
>> CREATE TEMPORARY TABLE foo AS
>> SELECT generate_series as bar
>> FROM generate_series(1, 1000000);
>>
>> CREATE INDEX idx_foo_bar ON foo (bar);
>>
>>
>> SELECT *
>> FROM (
>> SELECT bar
>> FROM foo
>> ORDER BY bar asc
>> LIMIT 1
>> ) x
>> UNION ALL
>> SELECT *
>> FROM (
>> SELECT bar
>> FROM foo
>> ORDER BY bar desc
>> LIMIT 1
>> ) y;
>>
>> DROP TABLE foo;
>>
>
> Seems to me SELECT min(<column>), max(<column>) FROM deja.vu ; would also
> work.
>
>
> --
> *Melvin Davidson*
> I reserve the right to fantasize. Whether or not you
> wish to share my fantasy is entirely up to you.
>