title: Get data from table A according to Table B
body: <p>I need some help...</p>
  
  <p><strong>Table A (Operation)</strong></p>
  
  <pre><code>table_a_id
  data
  </code></pre>
  
  <p><strong>Table B (Operation meta data)</strong></p>
  
  <pre><code>table_b_id
  table_a_id
  data_field_id_1
  data_field_id_2
  data_field_id_3
  </code></pre>
  
  <p>The user can select on a dropdown:</p>
  
  <ul>
  <li>meta data fields 1 as multi select option, first entry is displayed
  as "empty"</li>
  <li>meta data fields 2 as multi select option, first entry is displayed as "empty"</li>
  </ul>
  
  <p>The user wants to get all operations which fits the multi select options.</p>
  
  <p><strong>My thoughts were as follow:</strong></p>
  
  <p>I need to get all rows from Table A, </p>
  
  <ul>
  <li>where table B data_field_id_1 IN (some ids) </li>
  <li>or table B data_field_id_2 IN (some ids) </li>
  <li>or table_a_id is NOT IN Table B </li>
  <li>or data_field_id_1 IS NULL </li>
  <li>or data_field_id_2 IS NULL </li>
  <li>or data_field_id_3 IS NULL</li>
  </ul>
  
  <p>Can anyone help me with this SQL query?
  I am getting more and more confused.</p>