MariaDB 10.2

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SELECT VERSION();


VERSION()


10.2.27-MariaDB-10.2.27+maria~jessie-log


DROP TABLE IF EXISTS `PH`;

CREATE TABLE IF NOT EXISTS `PH` (
  `id` SERIAL,
  `date_time` CHAR(8),
  `ma_vi_tri` CHAR(2),
  `PH` INT UNSIGNED
);
INSERT INTO `PH`
  (`date_time`, `ma_vi_tri`, `PH`)
VALUES
  ('02102019', '1a', '222'),
  ('02102019', '0a', '111'),
  ('02102019', '2a', '333'),
  ('04102019', '1a', '222'),
  ('04102019', '0a', '111'),
  ('04102019', '2a', '333');
SELECT
  `id`,
  `date_time`,
  `ma_vi_tri`,
  `PH`
FROM
  `PH`;


id
date_time
ma_vi_tri
PH


1
02102019
1a
222

2
02102019
0a
111

3
02102019
2a
333

4
04102019
1a
222

5
04102019
0a
111

6
04102019
2a
333


SELECT
  CONCAT(
    '{"date_time": "', `date_time`, '", "ma_vi_tri": ',
    REPLACE(
      GROUP_CONCAT(
        JSON_OBJECT(`ma_vi_tri`, `PH`)
      ),
    '},{',
    ', '
    ),
    '}'
  ) `JSON`
FROM
  `PH`
WHERE
  `date_time` = '02102019'
GROUP BY
  `date_time`;


JSON


{"date_time": "02102019", "ma_vi_tri": {"1a": 222, "0a": 111, "2a": 333}}

id	date_time	ma_vi_tri	PH
1	02102019	1a	222
2	02102019	0a	111
3	02102019	2a	333
4	04102019	1a	222
5	04102019	0a	111
6	04102019	2a	333