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CREATE TABLE friend
(`user_id` int, `friend_id` int)
;
INSERT INTO friend
(`user_id`, `friend_id`)
VALUES
(1, 3),
(2, 1),
(2, 4),
(1, 2)
;
CREATE TABLE users
(`user_id` int, `username` varchar(6), `password` varchar(7))
;
INSERT INTO users
(`user_id`, `username`, `password`)
VALUES
(1, 'elexis', '*******'),
(2, 'rooney', '*******'),
(3, 'wayne', '*******'),
(4, 'June', '*******')
;
SELECT f.*, u. username FROM friend f JOIN users u ON f.friend_id = u.user_id WHERE f.user_id = 1 AND f.`friend_id` NOT IN (SELECT user_id FROM friend WHERE friend_id = 1)
UNION
SELECT f.*, u.username FROM friend f JOIN users u ON f.user_id = u.user_id WHERE friend_id = 1
| user_id | friend_id | username |
|---|---|---|
| 1 | 3 | wayne |
| 2 | 1 | rooney |