Re: count distinct

FlameDance <FlameDance_at_gmx.de> wrote in message news:<cbcupc$o15$03$1_at_news.t-online.com>...
> Hi everyone,
>
> I need to know the number of distinct values of 4 columns of the same table.
> For one column I'd use this statement:
>
> select count (*) from (select distinct column1 from mytable);
>
> This requires a full table scan. For 4 columns I could issue this
> command 4 times, using a different column each time. That would amount
> to 4 time consuming full table scans.
>
> select count (*) from (select distinct column1 from mytable);
> select count (*) from (select distinct column2 from mytable);
> select count (*) from (select distinct column3 from mytable);
> select count (*) from (select distinct column4 from mytable);
>
> Is there a way to do this faster, ideally with just one full table scan?
>
> Stephan

select count(distinct column1), count(distinct column2) ... from mytable

hth Received on Thu Jun 24 2004 - 01:23:41 CDT