title: Querying ElasticSearch SQL filtering by @timestamp
body: <p>I want to perform a query using SQL syntax in elastic search using URL /_sql and use in the where clause a filter for dates. So far if in the body I use this query</p>
  
  <pre><code>{
      "query": "SELECT count(*) from logstash where Severity='ERROR'"
  }
  </code></pre>
  
  <p>I get some results, then if I try to filter by @timestamp</p>
  
  <pre><code>{
      "query": "SELECT Time from logstash where Severity='ERROR'  and '@timestamp' &gt; NOW() - INTERVAL 30 MINUTES"
  }
  </code></pre>
  
  <p>And instead of getting 0 in the count or a shorter number than before I simply get nothing if I remove the quotes around @timestamp there it raises an error (not expecting the @ symbol), and if I use timestamp then suggest me to use @timestamp as timestamp is not a valid field.</p>
  
  <p>How can I filter by @timestamp? Or how should I escape the @ symbol for the field?</p>