Re: SQL Brain Teaser

bainbridge_i_at_perc03_at_bgers.co.uk (Ian Bainbridge) wrote:

> I have a table Project_costs ( project_code, expenditure_code ......)
> There are 1-n items per project_code,expenditure_code combination.
>
> What I am trying to determine with one piece of SQL is the number of
> different expenditure_codes per project_code and ultimately the maximum
> of those counts returned.
>
> I know I could do a select distinct of project_code and then loop for
> each project_code find the number of distinct occurences of expedniture_code
> and track the maximum of those myself but I just feel it should be possible in
> one pass.

A couple of people suggested

     select project_code, count( distinct expenditure_code )
     from   PROJECT_COSTS
     group by  project_code ;

If you add "order by 2", you'll get your counts, and the last count will be the maximum count.

For a query that returns just the maximum count, I would use

     select max( count( distinct expenditure_code ) )
     from   PROJECT_COSTS
     group by  project_code ;