title: How to get SUCCESS in SqlSensor(Airflow) when my sql throws me a null value
body: <p>How I can get SUCCESS value in SqlSensor(Airflow) when my sql throws me a NULL value and if it gets some records then FAIL? Do I need to write my own SqlSensor, if so, then can you guide me how to do this?
  my SqlSensor:</p>
  <pre><code>sensor = SqlSensor(
      task_id='check_for_data_in_table',
      conn_id = O_CONN_ID,    
      timeout=3200,
      poke_interval=120,
      sql=&quot;&quot;&quot;
        select column_c from test_table where column_b = to_date(trunc(sysdate))
      &quot;&quot;&quot;,
      dag=dag)
  </code></pre>