title: Count and IN Clause Issue
body: <p>I have a table named as employee history and its structure is as follows.</p>
  
  <p>tbl_employee_history
  Structure</p>
  
  <pre><code>id|history_nr|history_value|employee_id
  1   82         83             1
  2   86         84             1 
  3   87         85             1
  4   603                       1
  5   82         83             2
  6   86         83             2
  7   87         83             2
  8   603        83             2
  </code></pre>
  
  <p>This is the dummy data for my table. Now I want to count all those employees whose history_nr is in 82,86,87,603 AND history_value should not be empty like in the above example the  count should be 1 as for employee id 2 all the values are not empty. This is my query for implementing the count. </p>
  
  <pre><code>SELECT count(employee_id) FROM tbl_employee_history where history_nr IN(82,86,87,603) AND history_value!=''
  </code></pre>
  
  <p>But what happens is the count returns me two values. 
  Thanks in advance. </p>