title: Take count of column after merging
body: <p>I have merged two dataframes and selected for only those rows when a column contains a specific value. Now, I want to count the number of occurrences the value in the column has after filtering for <code>beak</code>.</p>
  <p>Here's what I have tried:</p>
  <pre><code>SELECT 
      landbirds.size, landbirds.weight,landbirds.feather, sea_birds.beak
  FROM 
      land_birds
  INNER JOIN
      sea_birds
  ON
      land_birds.colour = sea_birds.colour
  WHERE beak LIKE '%long%'
  GROUP BY feather
  COUNT(feather) ASC;
  </code></pre>
  <p>However, this does not produce an additional column counting the different feather types i.e. <code>long</code>, <code>medium</code>, <code>short</code>.</p>
  <p>How can I effectively count the feather types after merging?</p>
  <p>Example data:</p>
  <pre><code>#landbirds
  ... colour   size   weight   feather
        W       M      12.2     Long
        Br      M      12.7     Long
        Br      S      15.4     Short
  ..
  </code></pre>
  <p>second table:</p>
  <pre><code>#seabirds
  ...  colour   beak     
        W       Long  
        Br      Medium 
        Br      Long    
  ..
  </code></pre>
  <p>Expected output:</p>
  <pre><code>#results based on data above
  feather   featherCount
  Long          1
  Short         1
  </code></pre>