title: In ADX, how do I flatten my data to filter out null values in a specific time window?
body: <p>I have data coming into ADX from a single device that looks like this:</p>
  <pre><code>+-----------------------------+----------+-----------+-------------+
  | dateTime                    | latitude | longitude | temperature |
  +-----------------------------+----------+-----------+-------------+
  | 2020-07-17T20:55:00.824313Z | 47.5783  | -78.1692  |             |
  +-----------------------------+----------+-----------+-------------+
  | 2020-07-17T20:55:00.824311Z |          |           | 60          |
  +-----------------------------+----------+-----------+-------------+
  | 2020-07-17T20:54:01.000258Z | 47.5653  | -78.2692  |             |
  +-----------------------------+----------+-----------+-------------+
  | 2020-07-17T20:53:00.877956Z |          |           | 62          |
  +-----------------------------+----------+-----------+-------------+
  </code></pre>
  <p>Every other update from this source either contains the lat/long or the device's temperature.</p>
  <p>If I want to get a snapshot of the device's complete state in a given time window, how do I flatten this data? For instance, if I wanted the latest device state, I'd like to get back a single row that contains:</p>
  <pre><code>+-----------------------------+----------+-----------+-------------+
  | dateTime                    | latitude | longitude | temperature |
  +-----------------------------+----------+-----------+-------------+
  | 2020-07-17T20:55:00.824313Z | 47.5783  | -78.1692  |      60     |
  +-----------------------------+----------+-----------+-------------+
  </code></pre>