On 09/02/2015 05:14 PM, Tom Smith wrote:
> Hi:
>
> I need to get the first and last tow in one sql like below
>
> select first(col1), last(col1) from table order by col1
>
> I saw some posting in wiki with a custom function (or C extention)
> to do this. Is it widely used and reliable?
> https://wiki.postgresql.org/wiki/First/last_(aggregate)
> <https://wiki.postgresql.org/wiki/First/last_%28aggregate%29>
>
> I am wondering why these two functions are not part of postgresql built-in
> functions as it has many use cases
>
> Thanks
But what I think you are looking for are the windowing functions as what
you propose breaks down pretty quickly with more complicated queries.