MYSQL count of count?

Question

I have a mysql table like:

id, visitorid, pageid

When a visitor hits the website it stores their visitor id and the page id as a row.

Answer 1

One way to do it is to wrap this query into another one:

SELECT COUNT(visid) FROM (
    SELECT COUNT(visid) AS cvisid, visid 
      FROM vislog 
  GROUP BY visid 
  HAVING cvisid = 2) AS c

But I think you need to get the histogram of visits: this can be done with PHP (assuming the query is the same as in the question):

$results = array();
// query preparation skipped, as it's obviously done by the OP himself
while ($row = $sth->fetch()) {
  $count = $row['cvisid'];
  if (isset($results[$count])) {
    $results[$count]++;
  }
  else {
    $results[$count] = 1;
  }
}

Or with MySQL itself:

SELECT cvisid, 
       COUNT(cvisid) AS cnt 
  FROM (
    SELECT visid,
           COUNT(visid) AS cvisid 
      FROM vislog 
  GROUP BY visid ) AS c
GROUP BY cvisid