====== Handling database access in a Wordpress plugin ======
[[https://codex.wordpress.org/Class_Reference/wpdb|Wpdb class]] [[https://developer.wordpress.org/reference/classes/wpdb/|BIS]] [[https://codex.wordpress.org/Data_Validation#Database|Data validation for SQL]]

=== Get many data ===
<code linenums>
	global $wpdb;
	$sql = "SELECT * FROM " . $wpdb->prefix . "table_name";
	$result = $wpdb->get_results( $sql );
</code>
[[https://developer.wordpress.org/reference/classes/wpdb/get_results/|get_results($query, $output)]]

=== Get one row of data ===
<code linenums>
	global $wpdb;
	$sql = "SELECT id_truc FROM " . $wpdb->prefix . "table_name WHERE id_truc=" . $_GET['id'];
	$result = $wpdb->get_row($sql, 'ARRAY_A');
</code>
[[https://developer.wordpress.org/reference/classes/wpdb/get_row/|get_row($query, $output, $y)]]
=== Get the DB prefix ===
<code linenums>
global $wpdb;

// Current site prefix
echo $wpdb->prefix;
</code>

==== Create table at plugin activation if it don't exist  ====
<code linenums>
// If in first plugin file
register_activation_hook( __FILE__ , array($this, 'initDatabase') );

// If not in first plugin file
register_activation_hook( ABSPATH . '/wp-content/plugins/atn/atn.php', array($this, 'initDatabase') );

// ...

	public function initDatabase()
	{
		global $wpdb;

		// First check if the table already exist
		$sql = "SHOW TABLES LIKE '" . $wpdb->prefix . "table_name'";
		$result = $wpdb->query( $sql );
		// echo $sql . ' = ' . $result . '<br>';

		if($result == 0)
		{
			// echo 'No table found, creating it...<br>';
			$sql = "CREATE TABLE `" . $wpdb->prefix . "table_name` (
			  `id_table_name` int(11) NOT NULL,
			  `filename` varchar(255) CHARACTER SET utf8 NOT NULL,
			  `category` int(11) NOT NULL,
			  `serial_numbers` text CHARACTER SET utf8 NOT NULL
			) ENGINE=InnoDB DEFAULT CHARSET=utf8;";
			$result = $wpdb->query( $sql );
			// echo $sql . ' = ' . $result . '<br>';

			$sql = "ALTER TABLE `" . $wpdb->prefix . "table_name`
			ADD PRIMARY KEY (`id_table_name`);";
			$result = $wpdb->query( $sql );
			// echo $sql . ' = ' . $result . '<br>';

			$sql = "ALTER TABLE `" . $wpdb->prefix . "table_name`
			MODIFY `id_service_technique` int(11) NOT NULL AUTO_INCREMENT;";
			$result = $wpdb->query( $sql );
			// echo $sql . ' = ' . $result . '<br>';
		}
	}
</code>