Joining Databases

[macca_25]

Hi all,
I was wondering if anyone could suggest a solution to the following?
Here is sthe code:

<?
$db_list = mysql_list_dbs($db);

while ($row = mysql_fetch_object($db_list)) {

if (preg_match("/pm_data_/i", $row->Database)) {
mysql_select_db($row->Database);

$query_test = mysql_query("SELECT pm_message_title FROM pm_messages ORDER BY pm_message_title DESC");
while ($row = mysql_fetch_array($query_test)) {
echo $row['pm_message_title'] . "<BR>";
}
}
}
?>

At the moment this is getting all the databases whose name contains part of the value "pm_data_".
All the databases that match that value have the same tables and table structures.
It then proceeds to do a query where it gets the values for the pm_message_title column. This all works fine but i want to order the output by pm_message_title.
When i try and ORDER BY it orders the results by the database in which it came from....i want to be able to order all the results irrespective of which database they came from.
Any ideas on how to do this, that is if you are able to do this at all?

Cheers,
macca

[bubblenut]

Well of course it's going to, you're running seperate queries for each database (as you would have to, you can't join accross databases). What you're going to have to do is rather than echoing the results imediately, place them into an array then sort the array and then display the results. This will mean a bit more processing in PHP but it's the only way to achieve the result.
HTH
Bubble

[macca_25]

Thanks for the reply Bubblenut.
That makes sense.

While i have your attention (and anyone elses) may i ask another question related to this.
Lets say i am getting these databases from the server would there be any major performance issues if i was selecting and then querying say 50 different databases as opposed to 100 or even 1000. The reason i ask this is because i want a different database for each client. Within each database there are several tables.

Any suggestions?
Cheers,
macca