The code example from this page shows how to make a MySQL SELECT with JOIN table of different database, using PDO.
The trick is to specify both the database name and table in the SQL query, by using the syntax: database_name.table_name.
- This method works if you use an user and password for connecting to MySQL that has access to both databases.

Complete code example

// Data for connecting to MySQL
$mysql =['host'=>'localhost', 'dbname'=>'db_1', 'user'=>'root', 'pass'=>'password'];

//connects with PDO 
try {
  $conn = new PDO('mysql:host='. $mysql['host'] .'; dbname='. $mysql['dbname'], $mysql['user'], $mysql['pass']);
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); //set the PDO error mode to exception
}
catch(PDOException $e){ exit('Connection failed: '. $e->getMessage());}

$sql ="SELECT t1.id, t1.name, t2.col_db2 FROM db_1.table1 AS t1
 LEFT JOIN db_2.table2 AS t2 ON t1.id = t2.id";
$stmt = $conn->query($sql);

if($stmt !== false) {
  //shows selected data
  foreach($stmt as $row) {
    echo $row['id'] .'--'. $row['name'] .'--'. $row['col_db2'] .'<br>';
  }
}
else {
  echo '0 results';
}
- In this way you can join multiple tables from different databases.

Daily Test with Code Example

HTML
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PHP-MySQL
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src href rel
<a href="http://coursesweb.net/" title="CoursesWeb.net">CoursesWeb.net</a>
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font-family text-decoration font-size
h2 {
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What instruction selects all the <div> tags with class="cls"?
querySelector("div.cls") getElementsByTagName("div") querySelectorAll("div.cls")
var elm_list = document.querySelectorAll("div.cls");
var nr_elms = elm_list.length;       // number of selected items
alert(nr_elms);
Indicate the function that can be used to get the sum of values in an array.
array_sum() array_diff() array_shift()
$arr = array(1, 2, 3, 4);
$arr_sum = array_sum($arr);
echo $arr_sum;       // 10
Mysql SELECT JOIN tables on two different Databases

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