title: Select * from table1 that does not exist in table2 with conditional
body: <p>I have 2 tables.  One is a table with things that can be learned.  There is a JID that desribes each kind of row, and is unique to each row.  The second table is a log of things that have been learned (the JID) and also the userid for the person that learned it.  I am currently using this to select all of the data for the JID, but only the ones the user has learned based on userid.</p>
  
  <pre><code>SELECT * 
  FROM tablelist1
  LEFT JOIN tablelog2 ON (tablelist1.JID = tablelog2.JID) 
                         AND tablelog2.UID = 'php var'
  WHERE tablelog2.JID IS NOT NULL
  </code></pre>
  
  <p>I now need to select the rows of things to learn, but only the things the userid has NOT already learned.  I am obviously very new to this, bear with me. :)  I tried using IS NULL, but while it seems it works, it gives duplicate JID's one being NULL, one being correct.</p>