GROUP BY and ORDER BY in UNION - mysql

Question

I have this query:
SELECT category, description, price, date_added, datetime_created
FROM vc_expense
WHERE trip_id=? AND description LIKE ?
GROUP BY description, price
UNION SELECT category, description, NULL, NULL, NULL
FROM vc_expense_default
WHERE description LIKE ?
ORDER BY CASE
WHEN description LIKE ? AND price THEN 1
WHEN price THEN 2
ELSE 3
END, date_added DESC, datetime_created DESC
LIMIT 5
My problem is that when I GROUP the description+price on row #4, it doesn't take into account that I want the most recent results:
date_added DESC, datetime_created DESC
Is there a way to use ORDER BY after row #4 so I can get the newest items only, it doesn't seem to work because of the UNION
Thanks!
Edit:
The UNION was irrelevant, I just had put it inside parantheses, and get the latest items only from each group, like this:
SELECT e1.category, e1.description, e1.price, e1.date_added, e1.datetime_created
FROM vc_expense e1
LEFT JOIN vc_expense e2 ON (
e1.description=e2.description AND
e1.price=e2.price AND
e1.date_added < e2.date_added
)
WHERE e2.id IS NULL AND e1.trip_id = ? AND e1.description LIKE ?

Answer 1

From the docs:
https://dev.mysql.com/doc/refman/5.7/en/union.html
Use of ORDER BY for individual SELECT statements implies nothing about
the order in which the rows appear in the final result because UNION
by default produces an unordered set of rows
and here's what you need:
To apply ORDER BY or LIMIT to an individual SELECT, place the clause
inside the parentheses that enclose the SELECT:
(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10) UNION (SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);