如何在PHP中连接mysql中的两列

$servername = "localhost"; // MySQL服务器地址
$username = "username"; // MySQL用户名
$password = "password"; // MySQL密码
$dbname = "database"; // 数据库名称

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

$sql = "SELECT * FROM table1 JOIN table2 ON table1.column1 = table2.column2";

$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 遍历查询结果
    while ($row = $result->fetch_assoc()) {
        // 处理每一行数据
        echo "列1: " . $row["column1"] . " - 列2: " . $row["column2"] . "<br>";
    }
} else {
    echo "没有结果";
}

// 关闭连接
$conn->close();