title: SQL with group by and number of rows
body: <p>I have one table:</p>
  
  <pre><code>ID | domain       | address
  =======================================
   1 | example.com  | example.com/siteA
   2 | example.com  | example.com/siteB
   3 | example.com  | sub.example.com
   4 | example.com  | sub.example.com/dir
   5 | foobar.com   | foobar.com/site123
   6 | foobar.com   | foobar.com/site
   ...
  </code></pre>
  
  <p>now I like to know how many "addresses" one domain has like</p>
  
  <pre><code>ID | domain       | count
  ==========================
   1 | example.com  | 4
   5 | foobar.com   | 4
  </code></pre>
  
  <p>my statement is currently</p>
  
  <pre><code>SELECT * FROM table GROUP BY domain
  </code></pre>
  
  <p>I know this is nothing but is one table enough or should I split it into two?</p>