สอบถามเรื่อง เชื่อม 3 ตาราง Every derived table must have its own alias

SELECT tb.* FROM
(
	SELECT a.*  ,  b.stock_idcode as x  , c.stock_idcode_se as y
	FROM  `order`  as a
	LEFT JOIN `stock` as b ON (a.idcode = b.stock_idcode)
	LEFT JOIN `stock_se` as c ON (a.idcode = c.stock_idcode_se)
) As tb
WHERE tb.x IS null AND tb.y IS null

SELECT * FROM `order` 
LEFT JOIN `stock`  ON (order.idcode = stock.stock_idcode) AND (stock.stock_idcode IS null) 
LEFT JOIN `stock_se` ON (order.idcode = stock_se.stock_idcode_se) AND (stock_se.stock_idcode_se IS null)

select idcode 
from `order` as o
where not exists (select stock_idcode from `stock` where stock_id_code = o.idcode)
and not exists( select stock_idcode_se from `stock_se` where stock_idcode_se=o.idcode)