Question

I have databases of users and each has tables. I want to loop through each user and find the number of rows of a particular table common to each. So i connect to the first DB(usersDB) and pick the names of other DB’s from a table(userinfo) row(user_name). I then connect to each DB using the names obtained in userinfo and try to find the number of rows they each have on a particular table(products) common to them. I tried this but shows the same number of rows for all of them. Any help??

<?php
  //db parameters
 $dbhost = "localhost";   
 $dbname = "usersDB";
$dbuser = "root";   
$dbpass = ""; 

mysql_connect($dbhost, $dbuser, $dbpass) or die("MySQL Error: " . mysql_error());  
mysql_select_db($dbname) or die("MySQL Error: " . mysql_error());  


 //select main db
 $query  = "SELECT user_name FROM userinfo";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_BOTH))
  {
$dbName =$row['user_name'];
  mysql_connect($dbhost, $dbuser, $dbpass) or die("MySQL Error: " . mysql_error());  
  mysql_select_db("dbprefix_".$bName) or die("MySQL Error: " . mysql_error()); 

// do a query for each db
    $query = mysql_query('SELECT * FROM `products`');        
    $num_rows = mysql_num_rows($query);
   echo $dbName." has".$num_rows."products"."<br/>";
} 
  ?>

Answer 1

this may not be your issue but I noticed you arn’t closing the connection to each database after you query from it. you should assign a variable to mysql_select_db and after you echo close the database like this:

$conn = mysql_connect($dbhost, $dbuser, $dbpass) or die("MySQL Error: " . mysql_error());  
while($row = mysql_fetch_array($result, MYSQL_BOTH)){
   $dbName =$row['user_name'];
   $db = mysql_select_db("dbprefix_".$dbName, $conn) or die("MySQL Error: " . mysql_error()); 
    if( $db ){
        // do a query for each db
        $query = mysql_query('SELECT * FROM `products`');        
        $num_rows = mysql_num_rows($query);
        echo $dbName." has".$num_rows."products"."<br/>";

        mysql_close( $db );
    }
} 

also notice I took the mysql_connect() line out of the while loop because you don’t need to call this more than once. and I added the $conn variable for your mysql_connect() command, this way you can use $conn in your mysql_select_db() statement. This tell the select_db statement which connection to look in for this database (just alittle more secure).