Counting distinct rows - Mailing list pgsql-novice

Hi,

I'm having problems counting the number of distinct rows in a table.

I've tried the following:

    select distinct on(id) count(id)  from basketupdates order by id desc;

but I get the error

    ERROR:  Attribute basketupdates.id must be GROUPed or used in an aggregate function

I think it should say "MUST NOT", as if I remove the aggregate it works fine.
So I don't think this is the way to go about it.

Can anyone tell how I should be going about counting the distinct ids in a table ?


Thanks
JohnT