MySQL: update a record, on duplicate key leave NEWER one, and delete OLDER one? See inside

Question

There is a table:

CREATE TABLE `mytable` (
`user_id` INT(10) UNSIGNED NOT NULL,
`thing_id` VARCHAR(100) NOT NULL DEFAULT '',
`lock_date` DATETIME NOT NULL,
`lock_id` VARCHAR(36) NOT NULL,
PRIMARY KEY (`user_id`,`thing_id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;

and some values there:

INSERT INTO mytable(user_id,thing_id,lock_date,lock_id)
VALUES
(51082,'299ac9ff-2b2b-102d-8ff6-f64c971398c3','2012-03-16 00:39:12','ec7b2008-6ede-11e1-aac2-5924aae99221'),
(108325,'299ac9ff-2b2b-102d-8ff6-f64c971398c3','2013-02-05 19:30:03','7c6de986-6edd-11e1-aac2-5924aae99221'),
(108325,'d90b354d-4b5f-11e0-9959-47117d41cf4b','2012-03-16 00:47:41','1c243032-6ee0-11e1-aac2-5924aae99221');

I want to delegate all records of user_id = 108325 to user_id = 51082, and if both users have an equal thing_id field, leave the newer one only (lock_date1 > lock_date2), so that I have following result:

51082,'299ac9ff-2b2b-102d-8ff6-f64c971398c3','2013-02-05 19:30:03','7c6de986-6edd-11e1-aac2-5924aae99221'
108325,'d90b354d-4b5f-11e0-9959-47117d41cf4b','2012-03-16 00:47:41','1c243032-6ee0-11e1-aac2-5924aae99221'

Note that 51082 now has a newer record: lock_date = '2013-02-05 19:30:03' instead of '2012-03-16 00:39:12'.

So, how can I update a row, and on duplicate key leave the newer one (by some particular field)?

Thanks!

Use `ON DUPLICATE KEY UPDATE` – Refugnic Eternium Feb 16 '13 at 11:21 — Refugnic Eternium, Feb 16 '13 at 11:21

score 1 · Answer 1 · answered Feb 16 '13 at 11:23

INSERT INTO
  mytable(user_id,thing_id,lock_date,lock_id)
VALUES
  (51082,'299ac9ff-2b2b-102d-8ff6-f64c971398c3','2012-03-16 00:39:12','ec7b2008-6ede-11e1-aac2-5924aae99221'),
  (108325,'299ac9ff-2b2b-102d-8ff6-f64c971398c3','2013-02-05 19:30:03','7c6de986-6edd-11e1-aac2-5924aae99221'),
  (108325,'d90b354d-4b5f-11e0-9959-47117d41cf4b','2012-03-16 00:47:41','1c243032-6ee0-11e1-aac2-5924aae99221')
ON DUPLICATE KEY UPDATE SET
  user_id = VALUES(user_id),
  lock_date = VALUES(lock_date),
  lock_id = VALUES(lock_id)

MySQL: update a record, on duplicate key leave NEWER one, and delete OLDER one? See inside

1 Answers1