SQL Challenge: Arbitrary Cross-tab

Folks,

I have a wierd business case. Annoyingly it has to be written in *portable*
SQL92, which means no arrays or custom aggregates. I think it may be
impossible to do in SQL which is why I thought I'd give the people on this
list a crack at it. Solver gets a free drink/lunch on me if we ever meet at
a convention.

The Problem: for each "case" there are from zero to eight "timekeepers"
authorized to work on the "case", out of a pool of 150 "timekeepers". This
data is stored vertically:

authorized_timekeepers:
case_id | timekeeper_id
213447 | 047
132113 | 021
132113 | 115
132113 | 106
etc.

But, a client's e-billing application wants to see these timekeepers displayed
in the following horizontal format:

case_id | tk1 | tk2 | tk3 | tk4 | tk5 | tk6 | tk7 | tk8
213447 | 047 | | | | | | | |
132113 | 021 | 115 | 106 | 034 | 109 | 112 | 087 |
etc.

Order does not matter for timekeepers 1-8.

This is a daunting problem because traditional crosstab solutions do not work;
timekeepers 1-8 are coming out of a pool of 150.

Can it be done? Or are we going to build this with a row-by-row procedural
loop? (to reiterate: I'm not allowed to use a custom aggregate or other
PostgreSQL "advanced feature")

--
Josh Berkus
Aglio Database Solutions
San Francisco