I have a MySQL database, with roughly 25-30 tables. Each table has about 4 columns, but anywhere from 10-80 rows. How can I use php to print count the number of rows in all the tables?
I've tried;

$sql_query = "SELECT * FROM laptops, desktops, netbooks";
$result = mysql_query($sql_query);
$rows = mysql_num_rows($result);
echo $rows;

with no luck...
Ideas?