title: How to select case when a string is not equal a value then make another field blank?
body: <p>I have some columns like" OrderfieldNumber, Purchaser, Item. I'd like to create a statement in which:
  case when the purchaser is not 'ABC', 'DEF', 'GHK' then the OrderFieldNumber is blank. My purpose is just want to show OrderFieldNumber with those buyers only, I want to ignore other buyers without using Filter function. I tried:</p>
  
  <pre><code>case
  when purchaser &lt;&gt; 'ABC' then OrderFieldNum = ' '
  when purchaser &lt;&gt; 'DEF' then OrderFieldNum = ' '
  when purchaser &lt;&gt; 'GHK' then OrderFieldNum = ' '
  ELSE purchaser end as FilteredOrderField
  </code></pre>
  
  <p>But it doesn't seem to work out.  </p>