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We have this multiple database and we need to connect all of them together. We are using relationship table to talk back and forth. Multiple database will help us to backup the project or version separately.
Registration database: User Log In
Project database: Number of projects under the Logged in user.
Version database: Number of versions under the selected Project
THE ISSUE
Because we are using 0 and 1, only one user can able to connect to the database at a time. What we need is like the one in the flowchart below. Multiple user can able to connect to the database and working on a different project > different versions.
Thanks!
Sidenote: We are open to try different approach
<?php
//database error message
$connect_error='We could not able to connect. Please try later';
// Registration table
$main = mysql_connect('localhost','root','',true) or die($connect_error);
mysql_select_db('registration-table', $main) ;
// Obtaining session id
if(isset($_SESSION['id'])===true){
$session = $_SESSION['id'];
// Filtering projects based on 0 and 1
$sql = mysql_query("SELECT * FROM project1_table where user_id = '$session' and database_active = '0'",$main);
$row = mysql_fetch_array($sql);
// Each Project has Versions
$project_id = $row['id'];
$sqli = mysql_query("SELECT * FROM version_table where project_id = '$project_id' and database_active ='0'",$main);
$emp = mysql_fetch_array($sqli);
// Fetching the database name
$db_name = $emp['database_name'];
$sub = mysql_connect('localhost','root','',true) or die($connect_error);
mysql_select_db("$db_name", $sub) ;
}
?>
First of all I would suggest you to use mysqli or PDO other then mysql , Because after PHP 5.5 version mysql function deprecated and therefore mysql function will not be available in future
Multiple DB connection in Mysql
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
mysql_query('select * from tablename', $dbh1);
mysql_query('select * from tablename', $dbh2);
Multiple connection using Mysqli
$link1 = new mysqli($hostname, $username, $password,$database1);
$link2 = new mysqli($hostname, $username, $password,$database2);
mysqli_query($link1,"SELECT * FROM table");
mysqli_query($link2,"SELECT * FROM table");
Multiple DB connection in PDO
$conn1 = new PDO("mysql:host=$hostname;dbname=database1", $username, $password);
$conn2 = new PDO("mysql:host=$hostname;dbname=database1", $username, $password);
$conn1->query("SELECT * FROM table");
$conn1->query("SELECT * FROM table");
$conn1 = mysqli_connect( $db_host, $db_user, $db_pass, $db_name );
$conn2 = mysqli_connect( $db_host2, $db_user2, $db_pass2, $db_name2 );
Let's say you have a database named chat1 and chat2, and a table named tbl_chat1 and tbl_chat2.
$sql1 = "SELECT `id`, `msgs` FROM `chat1` . `tbl_chat1`";
$sql2 = "SELECT `id`, `msgs` FROM `chat2` . `tbl_chat2`";
$result1 = mysqli_query($conn1, $sql1);
$result2 = mysqli_query($conn2, $sql2);
However you can achieve the backup of your database without having to connect to multiple databases OK.
I am using two different server and make connections in this page but getting data from only one server table. Can you please help me fetch data from both servers? Thanks in advance. How can I select two databases from different servers on single page in PHP?
<?php
$conn = mysql_connect("localhost", "trtxxxxxxxxxxdfg", "dfcxxxxxxxxxxfg");
mysql_select_db("xxxx", $conn);
$con2=mysql_connect("localhost","hi*********r","h*********7");
$db2=mysql_select_db("xzcxc", $con2);
$sql="select * from bids";
$exe=mysql_query($sql);
$rw=mysql_fetch_array($exe);
echo $rw['bidname'];
echo "</br>";
$sql2="select * from wp_cities";
$exe2=mysql_query($sql2);
$rw2=mysql_fetch_array($exe2);
echo "test".$rw2['city']; ?>
try this,
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
Then to query database 1 pass the first link identifier:
mysql_query('select * from tablename', $dbh1);
and for database 2 pass the second:
mysql_query('select * from tablename', $dbh2);
i hope it will be helpful
I have information spread out across a few databases and want to put all the information onto one webpage using PHP. I was wondering how I can connect to multiple databases on a single PHP webpage.
I know how to connect to a single database using:
$dbh = mysql_connect($hostname, $username, $password)
or die("Unable to connect to MySQL");
However, can I just use multiple "mysql_connect" commands to open the other databases, and how would PHP know what database I want the information pulled from if I do have multiple databases connected.
Warning : mysql_xx functions are deprecated since php 5.5 and removed since php 7.0 (see http://php.net/manual/intro.mysql.php), use mysqli_xx functions or see the answer below from #Troelskn
You can make multiple calls to mysql_connect(), but if the parameters are the same you need to pass true for the '$new_link' (fourth) parameter, otherwise the same connection is reused. For example:
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
Then to query database 1 pass the first link identifier:
mysql_query('select * from tablename', $dbh1);
and for database 2 pass the second:
mysql_query('select * from tablename', $dbh2);
If you do not pass a link identifier then the last connection created is used (in this case the one represented by $dbh2) e.g.:
mysql_query('select * from tablename');
Other options
If the MySQL user has access to both databases and they are on the same host (i.e. both DBs are accessible from the same connection) you could:
Keep one connection open and call mysql_select_db() to swap between as necessary. I am not sure this is a clean solution and you could end up querying the wrong database.
Specify the database name when you reference tables within your queries (e.g. SELECT * FROM database2.tablename). This is likely to be a pain to implement.
Also please read troelskn's answer because that is a better approach if you are able to use PDO rather than the older extensions.
If you use PHP5 (And you should, given that PHP4 has been deprecated), you should use PDO, since this is slowly becoming the new standard. One (very) important benefit of PDO, is that it supports bound parameters, which makes for much more secure code.
You would connect through PDO, like this:
try {
$db = new PDO('mysql:dbname=databasename;host=127.0.0.1', 'username', 'password');
} catch (PDOException $ex) {
echo 'Connection failed: ' . $ex->getMessage();
}
(Of course replace databasename, username and password above)
You can then query the database like this:
$result = $db->query("select * from tablename");
foreach ($result as $row) {
echo $row['foo'] . "\n";
}
Or, if you have variables:
$stmt = $db->prepare("select * from tablename where id = :id");
$stmt->execute(array(':id' => 42));
$row = $stmt->fetch();
If you need multiple connections open at once, you can simply create multiple instances of PDO:
try {
$db1 = new PDO('mysql:dbname=databas1;host=127.0.0.1', 'username', 'password');
$db2 = new PDO('mysql:dbname=databas2;host=127.0.0.1', 'username', 'password');
} catch (PDOException $ex) {
echo 'Connection failed: ' . $ex->getMessage();
}
I just made my life simple:
CREATE VIEW another_table AS SELECT * FROM another_database.another_table;
hope it is helpful... cheers...
Instead of mysql_connect use mysqli_connect.
mysqli is provide a functionality for connect multiple database at a time.
$Db1 = new mysqli($hostname,$username,$password,$db_name1);
// this is connection 1 for DB 1
$Db2 = new mysqli($hostname,$username,$password,$db_name2);
// this is connection 2 for DB 2
Try below code:
$conn = mysql_connect("hostname","username","password");
mysql_select_db("db1",$conn);
mysql_select_db("db2",$conn);
$query1 = "SELECT * FROM db1.table";
$query2 = "SELECT * FROM db2.table";
You can fetch data of above query from both database as below
$rs = mysql_query($query1);
while($row = mysql_fetch_assoc($rs)) {
$data1[] = $row;
}
$rs = mysql_query($query2);
while($row = mysql_fetch_assoc($rs)) {
$data2[] = $row;
}
print_r($data1);
print_r($data2);
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2',$dbh2);
mysql_query('select * from tablename', $dbh1);
mysql_query('select * from tablename', $dbh2);
This is the most obvious solution that I use but just remember, if the username / password for both the database is exactly same in the same host, this solution will always be using the first connection. So don't be confused that this is not working in such case. What you need to do is, create 2 different users for the 2 databases and it will work.
Unless you really need to have more than one instance of a PDO object in play, consider the following:
$con = new PDO('mysql:host=localhost', $username, $password,
array(PDO::ATTR_PERSISTENT => true));
Notice the absence of dbname= in the construction arguments.
When you connect to MySQL via a terminal or other tool, the database name is not needed off the bat. You can switch between databases by using the USE dbname statement via the PDO::exec() method.
$con->exec("USE someDatabase");
$con->exec("USE anotherDatabase");
Of course you may want to wrap this in a catch try statement.
You might be able to use MySQLi syntax, which would allow you to handle it better.
Define the database connections, then whenever you want to query one of the database, specify the right connection.
E.g.:
$Db1 = new mysqli('$DB_HOST','USERNAME','PASSWORD'); // 1st database connection
$Db2 = new mysqli('$DB_HOST','USERNAME','PASSWORD'); // 2nd database connection
Then to query them on the same page, use something like:
$query = $Db1->query("select * from tablename")
$query2 = $Db2->query("select * from tablename")
die("$Db1->error");
Changing to MySQLi in this way will help you.
You don't actually need select_db. You can send a query to two databases at the same time. First, give a grant to DB1 to select from DB2 by GRANT select ON DB2.* TO DB1#localhost;. Then, FLUSH PRIVILEGES;. Finally, you are able to do 'multiple-database query' like SELECT DB1.TABLE1.id, DB2.TABLE1.username FROM DB1,DB2 etc. (Don't forget that you need 'root' access to use grant command)
if you are using mysqli and have two db_connection file. like
first one is
define('HOST','localhost');
define('USER','user');
define('PASS','passs');
define('**DB1**','database_name1');
$connMitra = new mysqli(HOST, USER, PASS, **DB1**);
second one is
define('HOST','localhost');
define('USER','user');
define('PASS','passs');
define(**'DB2**','database_name1');
$connMitra = new mysqli(HOST, USER, PASS, **DB2**);
SO just change the name of parameter pass in mysqli like DB1 and DB2.
if you pass same parameter in mysqli suppose DB1 in both file then second database will no connect any more. So remember when you use two or more connection pass different parameter name in mysqli function
<?php
// Sapan Mohanty
// Skype:sapan.mohannty
//***********************************
$oldData = mysql_connect('localhost', 'DBUSER', 'DBPASS');
echo mysql_error();
$NewData = mysql_connect('localhost', 'DBUSER', 'DBPASS');
echo mysql_error();
mysql_select_db('OLDDBNAME', $oldData );
mysql_select_db('NEWDBNAME', $NewData );
$getAllTablesName = "SELECT table_name FROM information_schema.tables WHERE table_type = 'base table'";
$getAllTablesNameExe = mysql_query($getAllTablesName);
//echo mysql_error();
while ($dataTableName = mysql_fetch_object($getAllTablesNameExe)) {
$oldDataCount = mysql_query('select count(*) as noOfRecord from ' . $dataTableName->table_name, $oldData);
$oldDataCountResult = mysql_fetch_object($oldDataCount);
$newDataCount = mysql_query('select count(*) as noOfRecord from ' . $dataTableName->table_name, $NewData);
$newDataCountResult = mysql_fetch_object($newDataCount);
if ( $oldDataCountResult->noOfRecord != $newDataCountResult->noOfRecord ) {
echo "<br/><b>" . $dataTableName->table_name . "</b>";
echo " | Old: " . $oldDataCountResult->noOfRecord;
echo " | New: " . $newDataCountResult->noOfRecord;
if ($oldDataCountResult->noOfRecord < $newDataCountResult->noOfRecord) {
echo " | <font color='green'>*</font>";
} else {
echo " | <font color='red'>*</font>";
}
echo "<br/>----------------------------------------";
}
}
?>
I have two databases, primary and secondary.
on the same page I need to take the data from second base, but without losing the connection to the first base.
You can make multiple calls to mysql_connect(), but if the parameters are the same you need to pass true for the '$new_link' (fourth) parameter, otherwise the same connection is reused.
so then you have
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
Then to query database 1, do this:
mysql_query('select * from tablename', $dbh1);
and for database 2:
mysql_query('select * from tablename', $dbh2);
I have information spread out across a few databases and want to put all the information onto one webpage using PHP. I was wondering how I can connect to multiple databases on a single PHP webpage.
I know how to connect to a single database using:
$dbh = mysql_connect($hostname, $username, $password)
or die("Unable to connect to MySQL");
However, can I just use multiple "mysql_connect" commands to open the other databases, and how would PHP know what database I want the information pulled from if I do have multiple databases connected.
Warning : mysql_xx functions are deprecated since php 5.5 and removed since php 7.0 (see http://php.net/manual/intro.mysql.php), use mysqli_xx functions or see the answer below from #Troelskn
You can make multiple calls to mysql_connect(), but if the parameters are the same you need to pass true for the '$new_link' (fourth) parameter, otherwise the same connection is reused. For example:
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
Then to query database 1 pass the first link identifier:
mysql_query('select * from tablename', $dbh1);
and for database 2 pass the second:
mysql_query('select * from tablename', $dbh2);
If you do not pass a link identifier then the last connection created is used (in this case the one represented by $dbh2) e.g.:
mysql_query('select * from tablename');
Other options
If the MySQL user has access to both databases and they are on the same host (i.e. both DBs are accessible from the same connection) you could:
Keep one connection open and call mysql_select_db() to swap between as necessary. I am not sure this is a clean solution and you could end up querying the wrong database.
Specify the database name when you reference tables within your queries (e.g. SELECT * FROM database2.tablename). This is likely to be a pain to implement.
Also please read troelskn's answer because that is a better approach if you are able to use PDO rather than the older extensions.
If you use PHP5 (And you should, given that PHP4 has been deprecated), you should use PDO, since this is slowly becoming the new standard. One (very) important benefit of PDO, is that it supports bound parameters, which makes for much more secure code.
You would connect through PDO, like this:
try {
$db = new PDO('mysql:dbname=databasename;host=127.0.0.1', 'username', 'password');
} catch (PDOException $ex) {
echo 'Connection failed: ' . $ex->getMessage();
}
(Of course replace databasename, username and password above)
You can then query the database like this:
$result = $db->query("select * from tablename");
foreach ($result as $row) {
echo $row['foo'] . "\n";
}
Or, if you have variables:
$stmt = $db->prepare("select * from tablename where id = :id");
$stmt->execute(array(':id' => 42));
$row = $stmt->fetch();
If you need multiple connections open at once, you can simply create multiple instances of PDO:
try {
$db1 = new PDO('mysql:dbname=databas1;host=127.0.0.1', 'username', 'password');
$db2 = new PDO('mysql:dbname=databas2;host=127.0.0.1', 'username', 'password');
} catch (PDOException $ex) {
echo 'Connection failed: ' . $ex->getMessage();
}
I just made my life simple:
CREATE VIEW another_table AS SELECT * FROM another_database.another_table;
hope it is helpful... cheers...
Instead of mysql_connect use mysqli_connect.
mysqli is provide a functionality for connect multiple database at a time.
$Db1 = new mysqli($hostname,$username,$password,$db_name1);
// this is connection 1 for DB 1
$Db2 = new mysqli($hostname,$username,$password,$db_name2);
// this is connection 2 for DB 2
Try below code:
$conn = mysql_connect("hostname","username","password");
mysql_select_db("db1",$conn);
mysql_select_db("db2",$conn);
$query1 = "SELECT * FROM db1.table";
$query2 = "SELECT * FROM db2.table";
You can fetch data of above query from both database as below
$rs = mysql_query($query1);
while($row = mysql_fetch_assoc($rs)) {
$data1[] = $row;
}
$rs = mysql_query($query2);
while($row = mysql_fetch_assoc($rs)) {
$data2[] = $row;
}
print_r($data1);
print_r($data2);
$dbh1 = mysql_connect($hostname, $username, $password);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2',$dbh2);
mysql_query('select * from tablename', $dbh1);
mysql_query('select * from tablename', $dbh2);
This is the most obvious solution that I use but just remember, if the username / password for both the database is exactly same in the same host, this solution will always be using the first connection. So don't be confused that this is not working in such case. What you need to do is, create 2 different users for the 2 databases and it will work.
Unless you really need to have more than one instance of a PDO object in play, consider the following:
$con = new PDO('mysql:host=localhost', $username, $password,
array(PDO::ATTR_PERSISTENT => true));
Notice the absence of dbname= in the construction arguments.
When you connect to MySQL via a terminal or other tool, the database name is not needed off the bat. You can switch between databases by using the USE dbname statement via the PDO::exec() method.
$con->exec("USE someDatabase");
$con->exec("USE anotherDatabase");
Of course you may want to wrap this in a catch try statement.
You might be able to use MySQLi syntax, which would allow you to handle it better.
Define the database connections, then whenever you want to query one of the database, specify the right connection.
E.g.:
$Db1 = new mysqli('$DB_HOST','USERNAME','PASSWORD'); // 1st database connection
$Db2 = new mysqli('$DB_HOST','USERNAME','PASSWORD'); // 2nd database connection
Then to query them on the same page, use something like:
$query = $Db1->query("select * from tablename")
$query2 = $Db2->query("select * from tablename")
die("$Db1->error");
Changing to MySQLi in this way will help you.
You don't actually need select_db. You can send a query to two databases at the same time. First, give a grant to DB1 to select from DB2 by GRANT select ON DB2.* TO DB1#localhost;. Then, FLUSH PRIVILEGES;. Finally, you are able to do 'multiple-database query' like SELECT DB1.TABLE1.id, DB2.TABLE1.username FROM DB1,DB2 etc. (Don't forget that you need 'root' access to use grant command)
if you are using mysqli and have two db_connection file. like
first one is
define('HOST','localhost');
define('USER','user');
define('PASS','passs');
define('**DB1**','database_name1');
$connMitra = new mysqli(HOST, USER, PASS, **DB1**);
second one is
define('HOST','localhost');
define('USER','user');
define('PASS','passs');
define(**'DB2**','database_name1');
$connMitra = new mysqli(HOST, USER, PASS, **DB2**);
SO just change the name of parameter pass in mysqli like DB1 and DB2.
if you pass same parameter in mysqli suppose DB1 in both file then second database will no connect any more. So remember when you use two or more connection pass different parameter name in mysqli function
<?php
// Sapan Mohanty
// Skype:sapan.mohannty
//***********************************
$oldData = mysql_connect('localhost', 'DBUSER', 'DBPASS');
echo mysql_error();
$NewData = mysql_connect('localhost', 'DBUSER', 'DBPASS');
echo mysql_error();
mysql_select_db('OLDDBNAME', $oldData );
mysql_select_db('NEWDBNAME', $NewData );
$getAllTablesName = "SELECT table_name FROM information_schema.tables WHERE table_type = 'base table'";
$getAllTablesNameExe = mysql_query($getAllTablesName);
//echo mysql_error();
while ($dataTableName = mysql_fetch_object($getAllTablesNameExe)) {
$oldDataCount = mysql_query('select count(*) as noOfRecord from ' . $dataTableName->table_name, $oldData);
$oldDataCountResult = mysql_fetch_object($oldDataCount);
$newDataCount = mysql_query('select count(*) as noOfRecord from ' . $dataTableName->table_name, $NewData);
$newDataCountResult = mysql_fetch_object($newDataCount);
if ( $oldDataCountResult->noOfRecord != $newDataCountResult->noOfRecord ) {
echo "<br/><b>" . $dataTableName->table_name . "</b>";
echo " | Old: " . $oldDataCountResult->noOfRecord;
echo " | New: " . $newDataCountResult->noOfRecord;
if ($oldDataCountResult->noOfRecord < $newDataCountResult->noOfRecord) {
echo " | <font color='green'>*</font>";
} else {
echo " | <font color='red'>*</font>";
}
echo "<br/>----------------------------------------";
}
}
?>