Re: SQL Challenge: Arbitrary Cross-tab

On Tue, 17 Aug 2004, Josh Berkus wrote:

> 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

If you know it's max 8, I think it may be possible, but I can't think of a
way that'd be better than just writing code yourself.

Just maybe something like the following would give you three timekeepers:
select foo.case_id, foo.v1, foo.v2, (select min(timekeeper_id) from
authorized_timekeepers where
authorized_timekeepers.case_id=foo.case_id and timekeeper_id > foo.v2) as
v3 from (
select foo.case_id, foo.v1, (select min(timekeeper_id) from
authorized_timekeepers where
authorized_timekeepers.case_id=foo.case_id and timekeeper_id > foo.v1) as
v2
from
(select foo.case_id, foo.v1 from
(select foo.case_id,
(select min(timekeeper_id) from authorized_timekeepers where
authorized_timekeepers.case_id=foo.case_id) as v1
from (select distinct case_id from authorized_timekeepers) foo
) foo) foo) foo;

If that works for 3 (and I think that's standard behavior), then you
should be able to extend it to any fixed number using the pattern.