How to store a key and value in a table from a JSON object in MySQL

问题

I'm having a MySQL database tables namely ds_message and ds_params, it table ds_message contains a JSON object in each row. I would like to store the key and value of a JSON object into the table ds_params for all the records by referring the ds_message primary key id

Table: ds_message

_____________________________________________________________________________________
id  key_value
_____________________________________________________________________________________
1  '{"a":"John", "b":"bat", "c":"$10"}'
2  '{"i":"Emma", "j":"Jam"}'

I'm required to insert the key_value into another table like

_________________________________________________
id   message_id    json_key    json_value
_________________________________________________
1    1             'a'         'John'
2    1             'b'         'bat'
3    1             'c'         '$10'
4    2             'i'         'Emma'
5    2             'j'         'Jam'

Table Structure:

CREATE TABLE `ds_message` (
  `id` int NOT NULL,
  `key_value` varchar(500) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='';

ALTER TABLE `ds_message`
  ADD PRIMARY KEY (`id`);

INSERT INTO `ds_message` (`id`, `key_value`) VALUES
(1, '{"a":"John", "b":"bat", "c":"$10"}');

INSERT INTO `ds_message` (`id`, `key_value`) VALUES
(2, '{"i":"Emma", "j":"Jam"}');

CREATE TABLE `ds_params` (
  `id` int NOT NULL,
  `message_id` int NOT NULL,
  `json_key` varchar(500) NOT NULL,
  `json_value` varchar(500) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='';

ALTER TABLE `ds_params`
  ADD PRIMARY KEY (`id`);

Kindly assist me how to achieve this, it may be a simple select cum insert statement or by stored procedure in an optimized way.

回答1:

Use MySql JSON functions. The following information will help you writing a stored procedure which fills the table key_value from ds_message.

1. To get the key array of your object, use json_keys

    SELECT JSON_keys('{"foo": 1, "bar": 2}')
   

2. You can get the value of each property using a key

    SELECT JSON_EXTRACT('{"foo": 1, "bar": 2}', '$.foo');
   

3. Use a nested loop to iterate the ds_message records and iterate each json object using the above methods. Insert a record for each key in each object.

来源：https://stackoverflow.com/questions/57586827/how-to-store-a-key-and-value-in-a-table-from-a-json-object-in-mysql