Feature 1255 : improve sql

Replace in queries LIMIT N,M by LIMIT N OFFSET M

git-svn-id: http://piwigo.org/svn/trunk@4331 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/include/functions.php

@@ -596,8 +596,8 @@ function set_random_representant($categories)
 SELECT image_id
   FROM '.IMAGE_CATEGORY_TABLE.'
   WHERE category_id = '.$category_id.'
-  ORDER BY RAND()
-  LIMIT 0,1
+  ORDER BY '.DB_RANDOM_FUNCTION.'()
+  LIMIT 0 OFFSET 1
 ;';
     list($representative) = pwg_db_fetch_row(pwg_query($query));