Getting statistics from tables

Hi all:

    Let's say I have a table that keeps track of the pages that an user has
seen in my website, something like:


              Users   |   Pages
          -----------------------------
              pepe    |   index.html
              johnsen |   about.html
              paco    |   about.html
              paco    |   index.html
              pepe    |   download.html


    It's easy to see the last 5, or 10, or 15 pages that an user has seen,
or the last users that have viewed a page. But how can I find out the 5
most seen pages, or the 5 most frequent users? My first thought (to find
the most viewed pages) was to:

    1) "SELECT DISTINCT pages FROM <table>"
    2) For each page, "SELECT count(users) FROM <table> WHERE
pages='<page>'"
    3) Find out the 5 pages that have returned the highest counts.

    At which point I imagined the perfomance problems that all the above
would cause in a dynamic page (PHP) and said to myself "ew!!".
    Is there any other way? Any built-in function in Postgres that can do
this, perhaps?
    (I used pageviews just as an example; what I have is a number of
similar situations where I need to find out this kind of data, and in
all of them said data is updated dynamically and needs to be displayed
in real time).



                        Paulo Jan.
                        DDnet.