title: Case Statement with complex AND/OR not working as intended
body: <p>I am expecting this to return the value of 'C', but it is returning 'A'.  I cannot seem to figure out why this will not work as my logic looks sound.</p>
  
  <pre><code>DECLARE @WeekStartDay varchar(10)
  DECLARE @WeekEndDay varchar(10)
  SET @WeekStartDay = 'Saturday'
  SET @WeekEndDay = 'Saturday'
  
  
  
  SELECT
  
      CASE
  
          WHEN (
                  ((@WeekStartDay = 'Saturday') OR (@WeekStartDay = 'Sunday'))
                           AND 
                  ((@WeekEndDay &lt;&gt; 'Saturday') OR (@WeekEndDay &lt;&gt; 'Sunday'))
              )
              THEN 'A'
  
          WHEN (
                  ((@WeekEndDay = 'Saturday') OR (@WeekEndDay = 'Sunday'))
                          AND 
                  ((@WeekStartDay &lt;&gt; 'Saturday') OR (@WeekStartDay &lt;&gt; 'Sunday'))
              )
              THEN 'B'
          WHEN (
                  ((@WeekEndDay = 'Saturday') OR (@WeekEndDay = 'Sunday'))
                          AND 
                  ((@WeekStartDay = 'Saturday') OR (@WeekStartDay = 'Sunday'))
              ) 
              THEN 'C'
  
      END AS Result
  </code></pre>
  
  <p>My intended function is:</p>
  
  <p>I am trying to get it to deteremine</p>
  
  <p>IF the @WeekStartDay = Saturday or Sunday AND @WeekEndDay IS NOT Saturday or Sunday THEN 'A'</p>
  
  <p>IF the @WeekEndDay = Saturday or Sunday AND @WeekStartDay IS NOT Saturday or Sunday THEN 'B'</p>
  
  <p>IF @WeekStartDay AND @WeekEndDay BOTH = Saturday or Sunday THEN 'C'</p>
  
  <p>Hmmm from responses looks like my logic was way more off than I thought.</p>