title: How to select only the first rows for each unique value of a column?
body: <p>Let's say I have a table of customer addresses:</p>
  <pre class="lang-none prettyprint-override"><code>+-----------------------+------------------------+
  |         CName         |      AddressLine       |
  +-----------------------+------------------------+
  |  John Smith           |  123 Nowheresville     |
  |  Jane Doe             |  456 Evergreen Terrace |
  |  John Smith           |  999 Somewhereelse     |
  |  Joe Bloggs           |  1 Second Ave          |
  +-----------------------+------------------------+
  </code></pre>
  <p>In the table, one customer like John Smith can have multiple addresses.
  I need the <code>SELECT</code> query for this table to return only first row found where there are duplicates in 'CName'. For this table it should return all rows except the 3rd (or 1st - any of those two addresses are okay but only one can be returned).</p>
  <p>Is there a keyword I can add to the <code>SELECT</code> query to filter based on whether the server has already seen the column value before?</p>