On Wed, 27 Sep 2006, Dan Libby wrote:
> Background:
>
> I have a hierarchical table where I have coordinate data for only the leaf
> nodes. I therefore want to find the center of all the leaf nodes under a
> given parent node, and set the parent node coordinate to that center point.
>
> I can calcululate that center point using aggregate functions (min, max) to
> find the necessary x,y values. So my query would look something like this:
>
> update parent_table set col =
> (select (max(pnt[0])-min(pnt[0]))/2+min(pnt[0]) || ',' ||
> max(pnt[1])-max(pnt[1])/2+min(pnt[1]) from point_tmp where condition)
> where condition2 ;
>
> Where point_tmp.tmp is defined as a point column.
>
> However, when I try to do it, I get a similar error:
>
> column "col" is of type point but expression is of type text
>
> If the above task can be performed some other way, perhaps I don't require
> string concatenation....
I don't have 8.0.x to check, but there's likely a
point(double precision, double precision) function you can use.
