title: SQL query for cumulative frequency of list of datetimes
body: <p>I have a list of times in a database column (representing visits to a website).</p>
  
  <p>I need to group them in intervals and then get a 'cumulative frequency' table of those dates.</p>
  
  <p>For instance I might have:</p>
  
  <pre><code>9:01
  9:04
  9:11
  9:13
  9:22
  9:24
  9:28
  </code></pre>
  
  <p>and i want to convert that into</p>
  
  <pre><code>9:05 - 2
  9:15 - 4
  9:25 - 6
  9:30 - 7
  </code></pre>
  
  <p>How can I do that? Can i even easily achieve this in SQL? I can quite easily do it in C#</p>