從 MySQL 數據庫讀取數據

SELECT 語句用于從數據表中讀取數據:

SELECT column_name(s) FROM table_name

我們可以使用 * 號來讀取所有數據表中的字段：

SELECT * FROM table_name

使用 MySQLi

以下實例中我們從 myDB 數據庫的 MyGuests 表讀取了 id, firstname 和 lastname 列的數據并顯示在頁面上：

實例 (MySQLi - 面向對象)

<?php$servername = "localhost";$username = "username";$password = "password";$dbname = "myDB"; // 創建連接$conn = newmysqli($servername, $username, $password, $dbname);// Check connectionif($conn->connect_error){die("連接失敗: " . $conn->connect_error);}$sql = "SELECT id, firstname, lastname FROM MyGuests";$result = $conn->query($sql); if($result->num_rows > 0){// 輸出數據while($row = $result->fetch_assoc()){echo"id: " . $row["id"]. " - Name: " . $row["firstname"]. "" . $row["lastname"]. "<br>"; }}else{echo"0 成果";}$conn->close();?>

以上代碼解析如下:

首先,我們設置了 SQL 語句從 MyGuests數據表中讀取 id, firstname 和 lastname 三個字段.之后我們使用改 SQL 語句從數據庫中取出成果集并賦給復制給變量 $result.

函數 num_rows() 判斷返回的數據.

如果返回的是多條數據,函數 fetch_assoc() 將結合集放入到關聯數組并循環輸出. while() 循環出成果集,并輸出 id, firstname 和 lastname 三個字段值.

以下實例使用 MySQLi 面向過程的方式,效果類似以上代碼:

實例 (MySQLi - 面向過程)

<?php$servername = "localhost";$username = "username";$password = "password";$dbname = "myDB"; // 創建連接$conn = mysqli_connect($servername, $username, $password, $dbname);// Check connectionif(!$conn){die("連接失敗: " . mysqli_connect_error());}$sql = "SELECT id, firstname, lastname FROM MyGuests";$result = mysqli_query($conn, $sql); if(mysqli_num_rows($result) > 0){// 輸出數據while($row = mysqli_fetch_assoc($result)){echo"id: " . $row["id"]. " - Name: " . $row["firstname"]. "" . $row["lastname"]. "<br>"; }}else{echo"0 成果";}mysqli_close($conn);?>

使用 PDO (+ 預處理)

以下實例使用了預處理語句.

選取了 MyGuests 表中的 id, firstname 和 lastname 字段,并放到 HTML 表格中：

實例 (PDO)

<?phpecho"<table style='border: solid 1px black;'>";echo"<tr><th>Id</th><th>Firstname</th><th>Lastname</th></tr>"; classTableRowsextendsRecursiveIteratorIterator{function__construct($it){parent::__construct($it, self::LEAVES_ONLY); }functioncurrent(){return"<td style='width:150px;border:1px solid black;'>" . parent::current(). "</td>"; }functionbeginChildren(){echo"<tr>"; }functionendChildren(){echo"</tr>" . "\n"; }}$servername = "localhost";$username = "username";$password = "password";$dbname = "myDBPDO"; try{$conn = newPDO("mysql:host=$servername;dbname=$dbname", $username, $password); $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $stmt = $conn->prepare("SELECT id, firstname, lastname FROM MyGuests"); $stmt->execute(); // 設置成果集為關聯數組$result = $stmt->setFetchMode(PDO::FETCH_ASSOC); foreach(newTableRows(newRecursiveArrayIterator($stmt->fetchAll()))as$k=>$v){echo$v; }}catch(PDOException$e){echo"Error: " . $e->getMessage();}$conn = null;echo"</table>";?>