MySQL 8.0

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CREATE TABLE `prices_test` (
  `id` int(10) unsigned NOT NULL DEFAULT '0',
  `user_id` int(10) NOT NULL,
  `date_end` date DEFAULT NULL,
  `price` decimal(10,2) DEFAULT NULL
)
INSERT INTO `prices_test` VALUES ('2', '2', '2018-11-29', '30000.00')
, ('3', '6', '2018-07-29', '20000.00')
, ('4', '18', '2017-12-31', '3999.00')
,('7', '18', '2018-03-01', '10000.00')
, ('10', '6', null, '44000.00')
,('13', '62', '2018-08-26', '12000.00')
, ('16', '62', null, '36500.00')
, ('17', '68', '2014-06-15', '22000.00')
, ('18', '69', null, '36500.00')
, ('19', '60', null, '10000.00')
, ('20', '68', null, '30000.00')
SELECT t.* 
FROM prices_test t 
INNER JOIN (
  SELECT user_id, MAX(IFNULL(date_end, '2019-03-21')) AS date_end
  FROM prices_test GROUP BY user_id
) AS maxval  on t.user_id=maxval.user_id and t.date_end=coalesce(maxval.date_end,'2019-03-21')




id
user_id
date_end
price


2
2
2018-11-29
30000.00

7
18
2018-03-01
10000.00


select * from prices_test a
where id in (select max(id) from prices_test b where a.user_id=b.user_id)


id
user_id
date_end
price


2
2
2018-11-29
30000.00

7
18
2018-03-01
10000.00

10
6
null
44000.00

16
62
null
36500.00

18
69
null
36500.00

19
60
null
10000.00

20
68
null
30000.00

id	user_id	date_end	price
2	2	2018-11-29	30000.00
7	18	2018-03-01	10000.00
10	6	null	44000.00
16	62	null	36500.00
18	69	null	36500.00
19	60	null	10000.00
20	68	null	30000.00