Instrukcja SQL - SELECT odwrotność tego zapytania

Po prostu użyj tego zapytania:

SELECT * 
     FROM Guide where id NOT IN (
       SELECT Guide.id 
         FROM Guide
         INNER JOIN GuideAvailability ON Guide.id = GuideAvailability.guideId
         WHERE GuideAvailability.startDate IN (1377946800) 
         GROUP BY GuideAvailability.guideId 
         HAVING COUNT(DISTINCT GuideAvailability.id) = 1
      )