SUMming和在MySQL中通过UNION连接，并在PHP中使用ECHO显示

<?php
// 连接MySQL数据库
$servername = "数据库服务器地址";
$username = "用户名";
$password = "密码";
$dbname = "数据库名";
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 执行查询并使用UNION连接结果
$sql = "SELECT column_name FROM table1
        UNION
        SELECT column_name FROM table2";
$result = $conn->query($sql);

// 检查查询结果是否为空
if ($result->num_rows > 0) {
    // 输出每行数据
    while($row = $result->fetch_assoc()) {
        echo "列名: " . $row["column_name"]. "<br>";
    }
} else {
    echo "查询结果为空";
}

// 关闭数据库连接
$conn->close();
?>