title: Oracle APEX: Bar chart with multiple series
body: <p>I have problem with Bar chart (with multiple series) in Oracle Apex. For example i have created simple bar chart with two series (April, December) from emp table.</p>
  
  <p><a href="https://i.stack.imgur.com/yhP1N.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yhP1N.png" alt="enter image description here"></a></p>
  
  <p>Source for series is SQL query.</p>
  
  <p><strong>For April:</strong></p>
  
  <pre><code>select job, count(job) as "Number of employees" from emp where to_char(HIREDATE, 'MON') = 'APR' GROUP BY job
  </code></pre>
  
  <p><strong>For December:</strong></p>
  
  <pre><code>select job, count(job) as "Number of employees" from emp where to_char(HIREDATE, 'MON') = 'DEC' GROUP BY job
  </code></pre>
  
  <p>Problem is that generated chart is not correct:</p>
  
  <p><a href="https://i.stack.imgur.com/xq3Kr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xq3Kr.png" alt="enter image description here"></a></p>
  
  <p>For Clerk there are no values in chart but there must be two emp. for December.
  This is output of mentioned queries from sql developer: </p>
  
  <p><strong>For April:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/W4M8y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/W4M8y.png" alt="enter image description here"></a></p>
  
  <p><strong>For December:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/WJYB1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WJYB1.png" alt="enter image description here"></a></p>
  
  <p>There is no problem when i use only one serie, problem is only with multiple series. I use Apex 5.1 with Oracle 12c.</p>