title: Have Prometheus send a SQL Query
body: <p>I'm trying to use <a href="https://prometheus.io/" rel="nofollow noreferrer">Prometheus</a> to monitor my MySQL database but can't seem to find an area to add SQL queries. For example, I'd like to run a SQL query which returns a value and then add that value to the graph/send an alert. Is there a way to have Prometheus send SQL queries and retrieve the output?</p>
  
  <p>Thank you</p>