Re: Question on collapsing a sparse matrix

On Mon, Apr 27, 2009 at 4:09 PM, Bryan Emrys <bryan(dot)emrys(at)gmail(dot)com> wrote:

> I've been handed a table that reminds me of a sparse matrix and I'm
> thinking that there should be some SQL way to simplify it.
> Assume table like (a column for every department, separate rows for each
> state if any department has headcount in the state, but each row has only
> one headcount entry):
>
> State Dept1 Dept2 Dept3 Dept4
> AZ 3 NULL NULL NULL
> AZ NULL 2 NULL NULL
> AZ NULL NULL 17 NULL
> CA 2 NULL NULL NULL
> CA NULL 21 NULL NULL
> CA NULL NULL NULL 6
> CA NULL NULL 4 NULL
> etc
>
> I'm trying to get to
>
> State Dept1 Dept2 Dept3 Dept4
> AZ 3 2 17 NULL
> CA 2 21 4 6
> etc
>
> Is there some way of rolling up or ANDing records so that I can sum each
> state into a single record per state? This looks like something that would
> be obvious, but I'm apparently missing it. Any pointers would be
> appreciated.
>
> (BTW, there are a couple hundred departments in the actual table, they are
> not conveniently numbered and as you may guess from the example, there is
> not a consistent number of rows for each state; some have only 1 row, some
> have 40 or more, it simply depends on how many departments have headcount in
> that state.)
>

select State,sum(Dept1),sum(Dept2),sum(Dept3),sum(Dept4) from yourtable
group by State;

Sean