Looping through mysql database

I have series of mysql databases on my server. The names of these data开发者_StackOverflowbases are stored in a separate database table (users) - column(dbname) . I want to loop through table (users), get the dbnames, connect to each and perform an operation on each database. How do I perform such looping?

Some rough code. Not debugged or tested...

$masterDBHost = 'localhost';
$masterDBUser = 'username';
$masterDBPass = 'somethingSecret';
$masterDBName = 'theDBname';

$sqlToPerformOnEachDatabases = 'SELECT 1';

// Connect to the Master Database
if( !( $master = mysql_connect( $masterDBHost , $masterDBUser , $masterDBPass ) ) )
  die( 'MySQL Error - Cannot Connect to Master Server' );
if( !mysql_select_db( $masterDBName , $master ) )
  die( 'MySQL Error - Cannot Connect to Master Database' );

// Get the Other Databases to Connect to
$databases = mysql_query( 'SELECT * FROM `databaseTable`' , $master );

// Check your Results
if( !$databases || mysql_num_rows( $databases )==0 ){
  # Nothing to work with
  echo 'Unable to find Databases to Access';
}else{
  # Something to work with
  while( $d = mysql_fetch_assoc( $databases ) ){
    // Connect to the Client Server
    if( !( $temp = mysql_connect( $d['host'] , $d['user'] , $d['pass'] ) ) ){
      # Can't connect to the Server
      echo 'MySQL Error - Failed to connect to '.$d['host'].' as '.$d['user'];
    }elseif( !mysql_select_db( $d['base'] , $temp ) ){
      # Can't connect to the Database
      echo 'MySQL Error - Failed to connect to '.$d['base'].' on '.$d['host'].' as '.$d['user'];
    }elseif( !mysql_query( $sqlToPerformOnEachDatabases , $temp ) ){
      # Your Command, well, stuffed up
      echo 'MySQL Error - Your Command Stuffed Up';
    }else{
      # Your Command worked OK
      echo 'All Good!';
    }
    # Close the connection (probably not needed, but nice to do)
    @mysql_close( $temp );
  }
}

Version 2

Allows for keeping a connection if the same Host/User/Pass is used

Again, not debugged or tested.

$masterDBHost = 'localhost';
$masterDBUser = 'username';
$masterDBPass = 'somethingSecret';
$masterDBName = 'theDBname';

$sqlToPerformOnEachDatabases = 'SELECT 1';

// Connect to the Master Database
if( !( $master = mysql_connect( $masterDBHost , $masterDBUser , $masterDBPass ) ) )
  die( 'MySQL Error - Cannot Connect to Master Server' );
if( !mysql_select_db( $masterDBName , $master ) )
  die( 'MySQL Error - Cannot Connect to Master Database' );

// Get the Other Databases to Connect to
$databases = mysql_query( 'SELECT * FROM `databaseTable`' , $master );

// Check your Results
if( !$databases || mysql_num_rows( $databases )==0 ){
  # Nothing to work with
  echo 'Unable to find Databases to Access';
}else{
  # Something to work with
  // A variable for the MySQL Connection
  $temp = false;
  // Declare some short-term memory
  $last = array();
  while( $d = mysql_fetch_assoc( $databases ) ){
    // Check Last Loop's details
    if( $temp
        && $last
        && array_diff( $last , $d ) ){
      // New Host, User or Pass
      @mysql_close( $temp );
      $last = false;
    }
    // Connect to the Client Server
    if( !$last
        && !( $temp = mysql_connect( $d['host'] , $d['user'] , $d['pass'] ) ) ){
      # Can't connect to the Server
      echo 'MySQL Error - Failed to connect to '.$d['host'].' as '.$d['user'];
    }elseif( !mysql_select_db( $d['base'] , $temp ) ){
      # Can't connect to the Database
      echo 'MySQL Error - Failed to connect to '.$d['base'].' on '.$d['host'].' as '.$d['user'];
    }elseif( !mysql_query( $sqlToPerformOnEachDatabases , $temp ) ){
      # Your Command, well, stuffed up
      echo 'MySQL Error - Your Command Stuffed Up';
    }else{
      # Your Command worked OK
      echo 'All Good!';
    }
    # Remember this Loop's details
    $last = $d;
  }
  @mysql_close( $temp );
}

After days of struggle I was able to come out with this solution. I took a lot of ideas from solutions that were provided to this question on this platform. the solutions themselves did not work for me but I had lots of ideas from them.

<?php

    //db parameters
    $dbhost = "myhost"; // this will ususally be 'localhost', but can sometimes differ  
    $dbname = "dbusers"; // the name of the database that you are going to use for this project  
    $dbuser = "root"; // the username that you created, or were given, to access your database  
    $dbpass = "mypassword"; // the password that you created, or were given, to access your database  


    // I first connect to the db with names of the other dbs 
    mysql_connect($dbhost, $dbuser, $dbpass) or die("MySQL Error: " . mysql_error());  
    mysql_select_db($dbname) or die("MySQL Error: " . mysql_error());  


    //select dbnames from the table with db names
    $query  = "SELECT dbname FROM users";
    $result = mysql_query($query);


    //loop through the results(dbname) and connect to each db 
    while($row = mysql_fetch_array($result, MYSQL_ASSOC))
    {
    //put the dbname results into a variable
    $dbName =$row['dbname'];
    // connect to each db
    $conn = mysql_connect($dbhost, $dbuser, $dbpass) or die("MySQL Error: " . mysql_error());  
    $db = mysql_select_db("mydbprefix_".$dbName) ;



       //do a query for each db this is because each db has same tables and structure
   //check to see if db exist
      if( $db ){

   //all the operation goes here in my case I wanted to count number of products for each table called products.
      $query2 = mysql_query("SELECT * FROM products");

    $num_rows = mysql_num_rows($query2);
    $pro = $num_rows;
    echo "this user has ".$pro." products"."<br/>";

    //another operation goes here for the same db.

    // then close connection for each db
    mysql_Close ($conn);
    }
     } 
    ?>

This was how I went around this problem. It might not be the best solution but this is what I have

i would do something like this, good luck! :

function dbConnect($location, $username, $password, $database) {
    $conn = mysql_connect($location, $username, $password); 
    if (!$conn) die ("Could not connect MySQL"); 
    mysql_select_db($database, $conn) or die ("Could not open database ".$database);
}
#######
# Connexion to databases containing users (add your own fields)
#######


dbConnect('localhost', 'root', '', 'databases');

$sql = "SELECT * FROM users";
$result = mysql_query($sql);
$numrows = mysql_num_rows($result);

#######
# Looping to establish connexion to db1 and db2
#######
while($row = mysql_fetch_array($result)) {
    dbConnect('localhost', $row["user"], $row["pass"], $row["db"]);
}

#######
# At this point, the connexion is established to LOCAHOST[DATABASES], LOCALHOST[DB1], LOCALHOST[DB2]
#######

$sql = "SELECT * FROM databases.users";
$result = mysql_query($sql);
$numrows = mysql_num_rows($result);
while($row = mysql_fetch_array($result)) {
    print "<pre>";
    print_r($row);
    print "</pre>";
}
/*
Array
(
    [id] => 1
    [user] => root
    [pass] => 
    [db] => db1
)
Array
(
    [id] => 2
    [user] => root
    [pass] => 
    [db] => db2
)
*/

$sql = "SELECT * FROM db1.infos";
$result = mysql_query($sql);
$numrows = mysql_num_rows($result);
while($row = mysql_fetch_array($result)) {
    print "<pre>";
    print_r($row);
    print "</pre>";
}
/*
Array
(
    [id] => 1
    [name] => John
    [age] => 26
)
Array
(
    [id] => 2
    [name] => Henri
    [age] => 34
)
*/

$sql = "SELECT * FROM db2.infos";
$result = mysql_query($sql);
$numrows = mysql_num_rows($result);
while($row = mysql_fetch_array($result)) {
    print "<pre>";
    print_r($row);
    print "</pre>";
}
/*
Array
(
    [id] => 1
    [name] => Paul
    [age] => 30
)
Array
(
    [id] => 2
    [name] => Scott
    [age] => 39
)
*/