Re: idea - new aggregates median, listagg

Thom Brown wrote:
> 2009/12/15 Pavel Stehule <pavel.stehule@gmail.com 
> <mailto:pavel.stehule@gmail.com>>
> 
>     Hello
> 
>     I am looking on new feature - ORDER clause in aggregate, and I thing,
>     so we are able to effectively implement some non standard, but well
>     known aggregates.
> 
>     a) function median - it is relative frequent request - with usually
>     slow implementation
> 
>     b) function listagg (it is analogy of group_concat from MySQL) - it
>     should simplify report generating and some other
> 
>     What is your opinion? Do you like to see these functions in core?
> 
> 
> 
> I'm probably missing the point here, but when I originally saw MySQL's 
> group_concat function, I found it odd that it featured ordering 
> functionality.  Shouldn't the order by determined by the query itself?  
> Otherwise it's almost as if its separating the relationship between the 
> result column and the resultset.

For xmlagg in particular, it is quite useful to be able order the 
results. And sorting the query doesn't work for ordering the agg unless 
you do it in a subquery. Oracle has this functionality and it is quite 
handy. It would be nice to see listagg with the option to order as well.

Scott