在 Google 饼图中按列值/类别对行进行分组

我有一个如下所示的表格：

sub_note | item_amount | sub_cat       |
---------------------------------------|
Spotify  |  $5.99      | entertainment |
Vodafone |  $35        | phone         |
Netflix  |  $5.99      | entertainment |

我想显示一个谷歌饼图，告诉我每个类别（即娱乐、电话等）花了多少钱。

我使用了以下对Google快速入门示例的改编，但我看到的只是一个带有"无数据"的空白图表。

<script type="text/javascript">
  // Load the Visualization API and the corechart package.
  google.charts.load('current', {'packages':['corechart']});
  // Set a callback to run when the Google Visualization API is loaded.
  google.charts.setOnLoadCallback(drawChart);
  // Callback that creates and populates a data table,
  // instantiates the pie chart, passes in the data and
  // draws it.
  function drawChart() {
    // Create the data table.
     var data = new google.visualization.DataTable();
    data.addColumn('string', 'Category');
    data.addColumn('number', 'Total');
    data.addRows([
     <?php 
     $query = "SELECT SUM(sub_amount) AS sub_cat, subs_total FROM subscriptions WHERE sub_user_id ='".$user_id."' GROUP BY sub_cat ORDER BY sub_cat";
      $exec = mysqli_query($connect,$query);
      while($row = mysqli_fetch_array($exec)){
      echo "['".$row['sub_cat']."',".$row['subs_total']."],";
      }
 ?>]);
    // Set chart options
    var options = {'title':'Spending by Category',
                   'width':600,
                   'height':400};
    // Instantiate and draw our chart, passing in some options.
    var chart = new google.visualization.PieChart(document.getElementById('chart_div'));
    chart.draw(data, options);
  }
</script>

很明显，查询代码及其分组方式有问题，但我正在努力解决这个问题。

任何指示都会很棒！

更新：感谢 SQL 更正的@WhiteHat，以下是功能代码：

<script type="text/javascript">
  // Load the Visualization API and the corechart package.
  google.charts.load('current', {'packages':['corechart']});
  // Set a callback to run when the Google Visualization API is loaded.
  google.charts.setOnLoadCallback(drawChart);
  // Callback that creates and populates a data table,
  // instantiates the pie chart, passes in the data and
  // draws it.
  function drawChart() {
    // Create the data table.
    var data = new google.visualization.DataTable();
    data.addColumn('string', 'Category');
    data.addColumn('number', 'Total');
    data.addRows([
     <?php 
     $query = "SELECT sub_cat, SUM(sub_amount) as subs_total FROM subscriptions WHERE sub_user_id ='".$user_id."' GROUP BY sub_cat ORDER BY sub_cat";
      $exec = mysqli_query($connect,$query);
      while($row = mysqli_fetch_array($exec)){
      echo "['".$row['sub_cat']."',".$row['subs_total']."],";
      }
   ?>]);
    // Set chart options
    var options = {'title':'How Much Pizza I Ate Last Night',
                   'width':600,
                   'height':400};
    // Instantiate and draw our chart, passing in some options.
    var chart = new google.visualization.PieChart(document.getElementById('chart_div'));
    chart.draw(data, options);
  }
</script>