MySQL Stored Proc build multidimensional JSON

Question

I have table with the following data structure:

name | age |     date    | value
---------------------------------
John | 20  |  2020-01-01 |   5
Peter| 21  |  2020-01-02 |  6.5
John | 26  |  2019-02-26 |  1.8
John | 20  |  2029-10-13 |  0.7
Peter| 47  |  2020-01-18 | 11.3
Peter| 21  |  2020-02-01 | 41.7
John | 20  |  2020-01-22 |   4

I want only by Mysql 5.5.5 Stored Proc(no json aggregate functions) to get result like this:

{
  "John (20)" : {
    ["2020-01-01", 5],
    ["2029-10-13", 0.7],
    ["2029-10-13", 4]
  },
  "John (26)" : {
    ["2019-02-26", 1.8]
  },
  "Peter (21)" : {
    ["2020-01-02", 6.5],
    ["2020-02-01", 41.7],
  },
  "Peter (47)" : {
    ["2020-01-18", 11.3]
  }
}

And can't figure out how to make it. Only getting flat json....

   select concat('[', group_concat(
   '{"name":"',`name`,'",',
   '"age":"',`age`,'",',
   '"date":"',`date`,'",',
   '"value":',`value`, '}' separator ','), ']') from `data`

Answer 1

One option:

SELECT
  CONCAT(
    '{',
    GROUP_CONCAT(
      CONCAT(
        `der`.`name_age`,
        ': {',
        `der`.`date_value`,
        '}'
      )
      SEPARATOR ', '),
    '}'
  ) `json_result`
FROM (
  SELECT
    CONCAT(
      '"',
      `name`,
      ' (', `age`, ')"'
    ) `name_age`,
    GROUP_CONCAT(
      CONCAT(
        '["',
        `date`,
        '", ',
        `value`,
        ']'
      )
      SEPARATOR ', ') `date_value`
  FROM
    `data`
  GROUP BY
    `name`, `age`
) `der`;

See dbfiddle.