title: Prometheus how to use multiple labels
body: <p>I have multiple crawls, how do I aggregate these results，Below is my example：</p>
  
  <p><code>{data="eth0",direction="sum",instance="localhost:21081",job="etha"} 111476
  {data="eth0",direction="sum",instance="localhost:21082",job="etha"} 29163
  {data="eth0",direction="sum",instance="localhost:21084",job="etha"} 10439</code></p>
  
  <p>I use the following statement, but no effect：</p>
  
  <pre><code>sum_over_time(eth0{data="eth0",direction="sum",job="eth0"}[20m])
  </code></pre>
  
  <p>Still there are multiple lines, I hope to be able to aggregate into one line</p>