Exclude extra unnecessary duplicate rows so the search is much faster

src/UNL/Catalog/CourseSearch/DBSearcher.php

@@ -4,7 +4,7 @@ class UNL_Catalog_CourseSearch_DBSearcher extends UNL_UndergraduateBulletin_Cour
 
     function getQueryResult($query, $offset = 0, $limit = -1)
     {
-        $query =  'SELECT DISTINCT courses.id, courses.xml FROM courses INNER JOIN crosslistings c1 ON courses.id=c1.course_id INNER JOIN crosslistings ON courses.id=crosslistings.course_id WHERE c1.courseNumber >= "500" AND (' . $query . ');';
+        $query =  'SELECT DISTINCT courses.id, courses.xml FROM courses INNER JOIN crosslistings c1 ON courses.id=c1.course_id INNER JOIN crosslistings ON courses.id=crosslistings.course_id WHERE c1.courseNumber >= "500" AND c1.courseNumber != crosslistings.courseNumber AND (' . $query . ');';
         return new UNL_UndergraduateBulletin_CourseSearch_DBSearchResults($query, $offset, $limit);
     }
 }
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