title: influxdb query: specify or filter tag by regex
body: <p>According to the <a href="https://docs.influxdata.com/influxdb/v1.2/query_language/data_exploration/#regular-expressions" rel="noreferrer">docs</a>, we can...</p>
  
  <blockquote>
    <p>Use a regular expression to specify a tag with a value in the WHERE clause.</p>
  </blockquote>
  
  <p>When I query my influxdb like this, I get the desired results.</p>
  
  <p><code>&gt; SELECT "field" FROM "measurement" WHERE tag = 19</code> </p>
  
  <p>When replacing the where filtering by a regex, however, I get no results.</p>
  
  <p><code>&gt; SELECT "field" FROM "measurement" WHERE tag =~ /19/</code> </p>
  
  <p>Can someone tell me why that is?</p>