title: Firebase query delete specific value from database
body: <p>I have this data on my firebase:</p>
  
  <pre><code>transportation: {
  "car" : {
      "bus" : {
        "toyota" : false,
        "bmw" : true
      },
      "suv" : {
        "honda" : false,
        "toyota" : true,
      }
    }
  }
  </code></pre>
  
  <p>I want to delete all child that have "false" value data so that my data looks like this:</p>
  
  <pre><code>transportation: {
      "car" : {
          "bus" : {
  
            "bmw" : true
          },
          "suv" : {
  
            "toyota" : true,
          }
        }
      }
  </code></pre>