SELECT * FROM `sortunion1`
UNION
SELECT * FROM `sortunion2`  

what I think is that when you are trying to query the above one it transforms it into query as follows


SELECT * FROM `sortunion1`
UNION
SELECT * FROM `sortunion2`  ORDER BY `sortunion2`.`id` DESC 
 LIMIT 0, 25

but instead if it transforms the same query as

SELECT * FROM `sortunion1`
UNION
(SELECT * FROM `sortunion2`  ORDER BY `sortunion2`.`id` DESC )
 LIMIT 0, 25

Then there won't be any issue.

Please tell me whether my understanding is correct or not. If yes,then I would like to take up the bug, else please suggest if there is any mistake in my approach.

Thanks,

Lakshit Arora