title: Inner join query returning empty set
body: <p>I have two tables with  varchar columns having common values. 
  I am trying to perform a simple inner join on the tables on those varchar columns but I am getting empty set as a result.<br>
  There are null values present in these columns.<br>
  Collation for both columns are same.<br>
  I googled for it but cant find a solution.<br>
  The query is a simple join query and doesn't have any syntax issues.<br>
  When I change the inner to left join I get a resultset but all the columns in the right table are empty even for the rows passes the join condition.  </p>
  
  <p>I created two dummy tables with a common varchar to run a join query and it works.
  So it is not a bug.So what are the possible reasons for getting empty sets any guesses.<br>
  The server is mysql version 5.5.37</p>
  
  <pre><code>update a set  a.id=x where a.col in(Select col from b where .....);
  </code></pre>
  
  <p>Another issue is that i have a query like above but when I run it It kind of hangs...On running 
      SHOW PROCESSLIST;
  the status is sending data...
  What does it mean?
  Can anyone help me.</p>
  
  <p>Edit 1
  The query is like this</p>
  
  <pre><code>UPDATE table1 bo INNER JOIN table2 ae 
  ON bo.joincol=ae.joincol AND ae.criteriaFieldName='UNSPSC' AND ae.taskId=4     AND ae.batchId = 44
  SET  bo.taskid=ae.taskId WHERE bo.procesId = 44 AND (taskid IS NULL OR taskid = 0);
  </code></pre>
  
  <p>Table1 contains 50+ columns<br>
  Table2 contains 8 columns<br>
  Unfortunately I can't disclose the data.
  Interesting fact is if I join them using taskId I get a resultset.</p>