Can I use MySql Create Select on two different servers with PHP?

Question

I am trying to use PHP and MySQL's Create Table Select between two different MySQL servers. I am not sure this can be done like this with SQL. I get no errors but I get nothing done either:

<?php
$dbname = 'cms';
$dbmaster = 'cmsms';

$db1 = mysql_connect('localhost', 'root', 'secret');
if (!$db1) {
    echo 'Could not connect to mysql';
    exit;
}

$db2 = mysql_connect('server2', 'root', 'secret');
if (!$db2) {
    echo 'Could not connect to mysql';
    exit;
}

mysql_select_db("$dbname", $db1) or die ("Unable to select database");
mysql_select_db("$dbmaster", $db2) or die ("Unable to select database");

$sql = "SHOW TABLES FROM $dbname";
$result = mysql_query($sql, $db1);

if (!$result) {
    echo "DB Error, could not list tables\n";
    echo 'MySQL Error: ' . mysql_error();
    exit;
}

while ($row = mysql_fetch_row($result)) {
    $sql = "DROP TABLE `$row[0]`";
    mysql_query($sql, $db1);
    echo "Table rows: {$row[0]} Deleted <br/>";
    $sql = "CREATE TABLE $row[0] SELECT * FROM $db2.$dbmaster.$row[0] ";
    mysql_query($sql, $db1);
    echo "Table: {$row[0]} created <br/>";

}
echo "<br/>done...";

mysql_free_result($result);
?>

That line:

$sql = "CREATE TABLE $row[0] SELECT * FROM $db2.$dbmaster.$row[0] ";

just doesn't work. the $db2 doesn't make it go to the other server and select.

From doing some reading on SO I found someone similar and someone said it could not be done and to look at federated tables, which will not work for me.

If this cannot be done above does anyone know a way to do what I am doing? I am dropping the tables on the copy and re-creating them based on the table in the master. Then I am selecting the data in the master to put in the re-created tables. Thank you

Update: Just so I can be clear. The code works if everything were on the same server and I only had one database connection. It is because of the create table select that I have problems, I believe. This SQL needs to use two servers at the same time. The create table is for one database that just dropped it's tables but the select is selecting from the database of the second connection - two connections in the same SQL statement.

Answer 1

Yes, on your PHP script you can perform all queries you want on all different servers you have access and permission to.

You don't specify your database on the $sql though. You specify it when you run the mysql_query function.

So, your code:

$sql = "SHOW TABLES FROM $dbname";
$result = mysql_query($sql, $db1);

Is wrong. It should only be:

$sql = "SHOW TABLES";
$result = mysql_query($sql, $db1);

By using $db1 on the second parameter of mysql_query you are already specifying that you want to show tables from that database only.

Following the same reasoning on the other sentences, you should be able to get results you want.

You won't be able to do this:

$sql = "CREATE TABLE $row[0] SELECT * FROM $db2.$dbmaster.$row[0] ";

If you want to insert rows from $db2 into newly created tables into $db1, you need to:

1. Run a query on $db2 to get results
2. Create table on $db1
3. Iterate $db2 results
4. Insert records on new table on $db1

There is no magic way of doing this in only one sentence.