SELECT  QuestionParentDirection ,
         QuestionChildDirection ,
         QuestionStyle ,
         QuestionTitle ,
         QuestionAnswer ,
         SourceCompany ,
         QuestionDate
 FROM    Question
 WHERE   ( Visibility = 1 )
         AND ( @QuestionParentDirection IS NULL
               OR RTRIM(QuestionParentDirection) = @QuestionParentDirection
             )
         AND ( @QuestionChildDirection IS NULL
               OR RTRIM(QuestionChildDirection) = @QuestionChildDirection
             )
         AND ( @QuestionStyle IS NULL
               OR RTRIM(QuestionStyle) = @QuestionStyle
             )
         AND ( @KeyWord IS NULL
               OR ( RTRIM(QuestionAnswer) LIKE '%' + @KeyWord + '%'
                    OR RTRIM(QuestionTitle) LIKE '%' + @KeyWord + '%'
                  )
             )
         AND ( @SourceCompany IS NULL
               OR RTRIM(SourceCompany) = @SourceCompany
             )
         AND ( QuestionDate BETWEEN @QuestionDateA
                            AND     @QuestionDateB )

------解决方案--------------------
从最内部的联接查询，或者说从最初的联接查询开始，一步一步看是否有数据。