PHP MySQL 读取数据

PHP MySQL 读取数据从 MySQL 数据库读取数据 SELECT 语句用于从数据表中读取数据:





SELECT column_name(s) FROM table_name我们可以使用 * 号来读取所有数据表中的字段：SELECT * FROM table_name如需学习更多关于 SQL 的知识，请访问我们的 SQL 教程。使用 MySQLi以下实例中我们从 myDB 数据库的 MyGuests 表读取了 id, firstname 和 lastname 列的数据并显示在页面上：实例 (MySQLi - 面向对象)<?php$servername = "localhost";$username = "username";$password = "password";$dbname = "myDB";// 创建连接$conn = new mysqli($servername, $username, $password, $dbname);// Check connectionif ($conn->connect_error) {die("连接失败:





" . $conn->connect_error);}$sql = "SELECT id, firstname, lastname FROM MyGuests";$result = $conn->query($sql);if ($result->num_rows > 0) {// 输出数据while($row = $result->fetch_assoc()) {echo "id:





" . $row["id"]. " - Name:





" . $row["firstname"]. " " . $row["lastname"]. "<br>";}} else {echo "0 结果";}$conn->close();?>以上代码解析如下:





首先，我们设置了 SQL 语句从 MyGuests数据表中读取 id, firstname 和 lastname 三个字段。之后我们使用改 SQL 语句从数据库中取出结果集并赋给复制给变量 $result。函数 num_rows() 判断返回的数据。如果返回的是多条数据，函数 fetch_assoc() 将结合集放入到关联数组并循环输出。 while() 循环出结果集，并输出 id, firstname 和 lastname 三个字段值。以下实例使用 MySQLi 面向过程的方式，效果类似以上代码:





实例 (MySQLi - 面向过程)<?php$servername = "localhost";$username = "username";$password = "password";$dbname = "myDB";// 创建连接$conn = mysqli_connect($servername, $username, $password, $dbname);// Check connectionif (!$conn) {die("连接失败:





" . mysqli_connect_error());}$sql = "SELECT id, firstname, lastname FROM MyGuests";$result = mysqli_query($conn, $sql);if (mysqli_num_rows($result) > 0) {// 输出数据while($row = mysqli_fetch_assoc($result)) {echo "id:





" . $row["id"]. " - Name:





" . $row["firstname"]. " " . $row["lastname"]. "<br>";}} else {echo "0 结果";}mysqli_close($conn);?>使用 PDO (+ 预处理)以下实例使用了预处理语句。选取了 MyGuests 表中的 id, firstname 和 lastname 字段，并放到 HTML 表格中：实例 (PDO)<?phpecho "<table style='border:





solid 1px black;'>";echo "<tr><th>Id</th><th>Firstname</th><th>Lastname</th></tr>";class TableRows extends RecursiveIteratorIterator {function __construct($it) {parent:





:





__construct($it, self:





:





LEAVES_ONLY);}function current() {return "<td style='width:





150px;border:





1px solid black;'>" . parent:





:





current(). "</td>";}function beginChildren() {echo "<tr>";}function endChildren() {echo "</tr>" . "\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();// 设置结果集为关联数组$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 "</table>";?>