Connessioni Multiple MySql

[luca200]

$host="localhost"; 
$user="root"; 
$pass="pw"; 
$link1 = mysqli_connect( $host, $user, $pass ) 
  or die("Impossibile connettersi al Database "); 

$sql=" SELECT * FROM db_1.tabella, db_2.tabella...... "
$count=mysqli_query($link1, $sql);