php初学(四)（中）--------读取mysql数据库

php 已经设置好php函数来链接mysql数据库。如果无法使用检查是否安装了php-mysql等模块。

数据库一般分为sql数据库与nosql数据库，mysql数据库处于sql数据库，需要学习sql语句掌握使用。

SELECT 语句用于从数据表中读取数据:

格式： SELECT column_name(s) FROM table_name
列子： SELECT * FROM table_name

MySQLi - 面向对象

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
 
// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($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();

MySQLi - 面向过程

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
 
// 创建连接
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$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);
?>

PDO 链接

<?php

 
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
 
try {
    
    
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $stmt = $conn->prepare("SELECT * FROM question"); 
    $stmt->execute();
   
    while($row = $stmt->fetchAll()) {
    
    
       
        var_dump($row);
    }
}
catch(PDOException $e) {
    
    
    echo "Error: " . $e->getMessage();
}
$conn = null;

?>