selecting unique values from a column

I have a MySQL table which contains the following type of information:

    Date            product 
2011-12-12           azd
2011-12-12           yxm
2011-12-10           sdx
2011-12-10           ssdd  

Here is an example of a script I use to get data from this table:

<?php

$con = mysql_connect("localhost","username","password");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
mysql_select_db("db", $con);
$sql=mysql_query("SELECT * FROM buy ORDER BY Date");
while($row = mysql_fetch_array($sql))
{

 echo "<li><a href='http://www.website/". $row['Date'].".html'>buy ". date("j, M Y", strtotime($row["Date"]))."</a></li>";

    }
    mysql_close($con);
?> 

This script displays every date from the table, e.g.

12.dec 2011
12.dec.2011
10.dec.2011
10.dec.2011

I would like to only display unique dates, e.g.

12.dec.2011
10.dec.2011

Answer

Use the DISTINCT operator in MySQL:

SELECT DISTINCT(Date) AS Date FROM buy ORDER BY Date DESC;