Hướng dẫn dùng mysql w3schools trong PHP


With PHP, you can connect to and manipulate databases.

MySQL is the most popular database system used with PHP.


What is MySQL?

  • MySQL is a database system used on the web
  • MySQL is a database system that runs on a server
  • MySQL is ideal for both small and large applications
  • MySQL is very fast, reliable, and easy to use
  • MySQL uses standard SQL
  • MySQL compiles on a number of platforms
  • MySQL is free to download and use
  • MySQL is developed, distributed, and supported by Oracle Corporation
  • MySQL is named after co-founder Monty Widenius's daughter: My

The data in a MySQL database are stored in tables. A table is a collection of related data, and it consists of columns and rows.

Databases are useful for storing information categorically. A company may have a database with the following tables:

  • Employees
  • Products
  • Customers
  • Orders

PHP + MySQL Database System

  • PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)

Database Queries

A query is a question or a request.

We can query a database for specific information and have a recordset returned.

Look at the following query (using standard SQL):

SELECT LastName FROM Employees

The query above selects all the data in the "LastName" column from the "Employees" table.

To learn more about SQL, please visit our SQL tutorial.


Download MySQL Database

If you don't have a PHP server with a MySQL Database, you can download it for free here: http://www.mysql.com


Facts About MySQL Database

MySQL is the de-facto standard database system for web sites with HUGE volumes of both data and end-users (like Facebook, Twitter, and Wikipedia).

Another great thing about MySQL is that it can be scaled down to support embedded database applications.

Look at http://www.mysql.com/customers/ for an overview of companies using MySQL.




Select Data From a MySQL Database

The SELECT statement is used to select data from one or more tables:

SELECT column_name(s) FROM table_name

or we can use the * character to select ALL columns from a table:

To learn more about SQL, please visit our SQL tutorial.


Select Data With MySQLi

The following example selects the id, firstname and lastname columns from the MyGuests table and displays it on the page:

Example (MySQLi Object-oriented)

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
  // output data of each row
  while($row = $result->fetch_assoc()) {
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "
";
  }
} else {
  echo "0 results";
}
$conn->close();
?>

Run example »

Code lines to explain from the example above:

First, we set up an SQL query that selects the id, firstname and lastname columns from the MyGuests table. The next line of code runs the query and puts the resulting data into a variable called $result.

Then, the function num_rows() checks if there are more than zero rows returned.

If there are more than zero rows returned, the function fetch_assoc() puts all the results into an associative array that we can loop through. The while() loop loops through the result set and outputs the data from the id, firstname and lastname columns.

The following example shows the same as the example above, in the MySQLi procedural way:

Example (MySQLi Procedural)

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
  // output data of each row
  while($row = mysqli_fetch_assoc($result)) {
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "
";
  }
} else {
  echo "0 results";
}

mysqli_close($conn);
?>

Run example »



You can also put the result in an HTML table:

Example (MySQLi Object-oriented)

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
  echo "

";
  // output data of each row
  while($row = $result->fetch_assoc()) {
    echo "";
  }
  echo "
IDName
".$row["id"]."".$row["firstname"]." ".$row["lastname"]."
";
} else {
  echo "0 results";
}
$conn->close();
?>

Run example »


Select Data With PDO (+ Prepared Statements)

The following example uses prepared statements.

It selects the id, firstname and lastname columns from the MyGuests table and displays it in an HTML table:

Example (PDO)

echo "

";
echo "";

class TableRows extends RecursiveIteratorIterator {
  function __construct($it) {
    parent::__construct($it, self::LEAVES_ONLY);
  }

  function current() {
    return "

";
  }

  function beginChildren() {
    echo "

";
  }

  function endChildren() {
    echo "

" . "\n";
  }
}

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDBPDO";

try {
  $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  $stmt = $conn->prepare("SELECT id, firstname, lastname FROM MyGuests");
  $stmt->execute();

  // set the resulting array to associative
  $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
  foreach(new TableRows(new RecursiveArrayIterator($stmt->fetchAll())) as $k=>$v) {
    echo $v;
  }
} catch(PDOException $e) {
  echo "Error: " . $e->getMessage();
}
$conn = null;
echo "

IdFirstnameLastname
" . parent::current(). "
";
?>

Run example »