自学教程ORDER BY 关键词用于对记录集中的数据进行排序。
ORDER BY 关键词
ORDER BY 关键词用于对记录集中的数据进行排序。
ORDER BY 关键词默认对记录进行升序排序。
如果你想降序排序，请使用 DESC 关键字。
语法
SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC
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下面的实例选取 "myguests" 表中存储的所有数据，并根据 "reg_date" 列对结果进行排序：
使用 MySQLi
MySQLi - 面向对象：
实例
<?php
$servername = "localhost";
$username = "root";
$password = "root";
$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 ORDER BY reg_date DESC";
//创建预处理语句
$stmt = $conn->prepare($sql);
//执行查询
$stmt->execute();
//获取查询结果
$result = $stmt->get_result();
if ($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：
实例
<?php
$servername = "localhost";
$username = "root";
$password = "root";
$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 ORDER BY reg_date DESC";
$stmt = mysqli_prepare($conn, $sql);
//执行查询
mysqli_stmt_execute($stmt);
//获取结果
$result = mysqli_stmt_get_result($stmt);
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
<?php
echo "<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 = "root";
$password = "root";
$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 ORDER BY reg_date DESC");
$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>";
?>根据两列进行排序
可以根据多个列进行排序。当按照多个列进行排序时，只有第一列的值相同时才使用第二列：
SELECT column_name(s)
FROM table_name
ORDER BY column1, column2
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