收到“警告：mysqli_fetch_array（）期望参数1为mysqli_result，..中给出的布尔值”错误

Question

正如标题所示，尝试在PHP中执行SQL查询时，我收到一个“警告：mysqli_fetch_array（）期望参数1为mysqli_result，..中给出的布尔值。”错误。

我的代码如下：

 // Create connection
 $conn = mysqli_connect($servername, $username, $password, $dbname);
 // Check connection
 if (!$conn) {
 die("Connection failed: " . mysqli_connect_error()); 

 }
 else{

 $sessionusername = $_SESSION["username"];

 $query = mysqli_query($conn,"SELECT * FROM APPOINTMENT WHERE username = $sessionusername");




while($row = mysqli_fetch_array($query))
{
echo "<tr>";
echo "<td class= 'inside-while'>" . $row['APNo'] . "</td>";
echo "<td class= 'inside-while'>" . $row['DNo'] . "</td>";
echo "<td class= 'inside-while'>" . $row['APDATE'] . "</td>";
echo "</tr>";
}

任何帮助将不胜感激。