title: Power Bi : if Condition with multiple cases specially with date = NULL or SYSDATE
body: <p>I have a table with these columns shipped_date, Promise_date </p>
  
  <p>Example (consider that the current date is today's date which is "20/6/2019"):</p>
  
  <pre><code>Shipped_date        Promise_date
  20/1/2019           15/1/2019
  Null                19/6/2019
  Null                25/6/2019
  </code></pre>
  
  <p>How can I make an if condition that gives output</p>
  
  <p>1- <code>if shipped_date = null and promise_date &lt; today's date then "yes"</code></p>
  
  <p>2- <code>if shipped_date = null and promise_date &gt;= today's date then "no"</code></p>
  
  <p>i tried to write Dax code but i succeded in another condition when shipped_date have value and promise_date is not today's date </p>
  
  <pre><code>if [JC_ShippedDate] &lt; [PromiseDate] then "Completed early"
  else if [JC_ShippedDate] &gt; [PromiseDate] then "Completed behind schedule"
  else if [JC_ShippedDate] = [PromiseDate] then "Completed on time" else "open"
  </code></pre>
  
  <p>error is </p>
  
  <pre><code>Expression.Error: We cannot convert the value null to type Logical.
  Details:
      Value=
      Type=Type
  </code></pre>