title: How can I count rows having distinct IP address per day?
body: <p>How can I count how many unique addresses have been on my site each day?
  My table looks like this:</p>
  
  <blockquote>
    <p>Row names: id, name, entity, ip_address, date  </p>
    
    <p>1,"Baldur","EntityA","85.221.18.251","2012-01-09 17:32:52"
    2,"Baldur","EntityB","85.221.18.251","2012-01-09 17:32:57"
    3,"Baldur","EntityB","85.221.18.252","2012-01-09 17:33:01"
    4,"Baldur","EntityA","85.221.18.253","2012-01-10 17:33:12"
    5,"Mango","EntityA","85.221.18.257","2012-01-10 17:32:52"
    6,"Baldur","EntityB","85.221.18.251","2012-01-10 17:32:57"
    7,"Mango","EntityB","85.221.18.253","2012-01-11 17:33:01"
    8,"Mango","EntityA","85.221.18.251","2012-01-11 17:33:12"
    9,"Mango","EntityA","85.221.18.253","2012-01-11 17:32:52"
    10,"Baldur","EntityB","85.221.18.255","2012-01-11 17:32:57"
    11,"Mango","EntityB","85.221.18.254","2012-01-11 17:33:01"
    12,"Mango","EntityA","85.221.18.251","2012-01-12 17:33:12"</p>
  </blockquote>
  
  <p>I'm thinking something along these lines:</p>
  
  <pre><code>SELECT date, COUNT(ip)
  FROM mytable
  GROUP BY date
  </code></pre>
  
  <p>This only gives me rows with count of one.</p>