title: What exactly is a wide column store?
body: <p>Googling for a definition either returns results for a column oriented DB or gives very vague definitions.</p>
  
  <p>My understanding is that wide column stores consist of column families which consist of rows and columns. Each row within said family is stored together on disk. This sounds like how row oriented databases store their data. Which brings me to my first question:</p>
  
  <p><strong>How are wide column stores different from a regular relational DB table?</strong> This is the way I see it:</p>
  
  <pre><code>* column family        -&gt; table
  * column family column -&gt; table column
  * column family row    -&gt; table row
  </code></pre>
  
  <p>This image from <em>Database Internals</em> simply looks like two regular tables:</p>
  
  <p><a href="https://i.stack.imgur.com/HzMbH.png" rel="noreferrer"><img src="https://i.stack.imgur.com/HzMbH.png" alt="Two column families, contents, and anchors"></a></p>
  
  <p>The guess I have as to what is different comes from the fact that "multi-dimensional map" is mentioned along side wide column stores. So here is my second question:</p>
  
  <p><strong>Are wide column stores sorted from left to right?</strong> Meaning, in the above example, are the rows sorted first by <code>Row Key</code>, then by <code>Timestamp</code>, and finally by <code>Qualifier</code>? </p>