From: hugo@perFact.REMOVETHIS.info.INVALID   
      
   On Thu, 21 Oct 2010 09:18:02 +0100, Andrew Morton wrote:   
      
   >Hugo Kornelis wrote:   
   >> On Tue, 19 Oct 2010 16:25:25 -0700, tshad wrote:   
   >>   
   >>>   
   >>> "Andrew Morton" wrote   
   >>>> tshad wrote:   
   >>>>> WHERE (@Status = 'ALL') OR ((@Status <> 'ALL') AND (dStart =   
   >>>>> (Select ...   
   >>>>   
   >>>> Unless my brain deceives me at this early hour,   
   >>>> A OR (NOT A AND B) is the same as A OR B.   
   >   
   >Umm... would I be wrong if @Status was NULL?   
      
   Yes, you would. If @Status is NULL, both @Status = 'ALL' and @Status <>   
   'ALL' evaluate to Unknown.   
   Unknown AND (dStart = ....) evaluates to either False or Unknown   
   (depends on the result of the second condition   
   Unknown OR (Unknown or False) evaluates to Unknown.   
      
   And since Unknown means the row is rejected, nothing will ever be   
   returned from this query when @Status is NULL.   
      
   I can't believe I overlooked that. :(   
      
   --   
   Hugo Kornelis, SQL Server MVP   
   My SQL Server blog: http://sqlblog.com/blogs/hugo_kornelis   
      
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