MySQL ORDER BY question

Question

Comment puis-je ajouter un ordre par users_friends.date_created qui régit les deux requêtes select.

Voici mon code MySQL.

(SELECT A.user_id, A.friend_id, B.username, B.avatar 
FROM users_friends AS A 
INNER JOIN users AS B 
ON A.friend_id = B.user_id 
AND A.user_id = 3 
AND A.friendship_status = 1) 
UNION 
(SELECT A.friend_id, A.user_id, B.username, B.avatar 
FROM users_friends AS A 
INNER JOIN users AS B 
ON B.user_id = A.user_id 
AND A.friend_id = 3 
AND A.friendship_status = 1) 
LIMIT 10 

Answer 1

Vous pouvez ajouter une sélection externe avec une commande par et envelopper le syndicat comme une table dérivée

SELECT user_id, friend_id, username, avatar FROM (
(SELECT A.user_id, A.friend_id, B.username, B.avatar 
FROM users_friends AS A 
INNER JOIN users AS B 
ON A.friend_id = B.user_id 
AND A.user_id = 3 
AND A.friendship_status = 1) 
UNION 
(SELECT A.friend_id, A.user_id, B.username, B.avatar 
FROM users_friends AS A 
INNER JOIN users AS B 
ON B.user_id = A.user_id 
AND A.friend_id = 3 
AND A.friendship_status = 1) 
LIMIT 10 
) C 
ORDER BY avatar 

Answer 2

Si vous sélectionnez la colonne date_created est également autorisée dans la requête alors nous pouvons commander l'union de les résultats que -

(SELECT A.user_id, A.friend_id, B.username, B.avatar, A.date_created as createdDate 
FROM users_friends AS A 
INNER JOIN users AS B 
ON A.friend_id = B.user_id 
AND A.user_id = 3 
AND A.friendship_status = 1) 
UNION 
(SELECT A.friend_id, A.user_id, B.username, B.avatar, A.date_created as createdDate 
FROM users_friends AS A 
INNER JOIN users AS B 
ON B.user_id = A.user_id 
AND A.friend_id = 3 
AND A.friendship_status = 1) 
order by createdDate LIMIT 10