I've run into this before, I ran into it today, and I'll probably run into it again.

Why isn't there an aggregate function that concatenates strings?

Besides the obvious "string don't get that big" (which I'd manage by manipulating my group by to fit) why not?

Something like:

CONCAT_AGG(column, separator)

Where separator is a varchar that determines what goes between each string (space, comma-space, whatever).

This would be pretty dang handy.